Patent Publication Number: US-2023157654-A1

Title: System for targeted medical intervention using a magnetic field

Description:
The present application is a continuation application of international PCT patent application No. PCT/CA2021/051776, filed on Dec. 10, 2021, which claims priority from U.S. provisional patent application No. 63/280,041 filed on Nov. 16, 2021, incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to targeted intervention in a subject using a magnetic field, and more particularly to targeted intervention in a subject using magnetotactic entities that are steered with a magnetic field. 
     BACKGROUND 
     Use of a magnetic field for medical interventions is becoming increasingly more prevalent. For instance, the following patent documents describe prior art medical applications harnessing a magnetic field: U.S. Pat. Nos. 9,655,539, 9,381,063, 9,220,425, 8,986,214, 8,684,010, 8,457,714, US20130006100, US20120310111, US20120289822, US20120288838, US20110092808, U.S. Pat. No. 7,873,401, US20100305402, US20090275828, US20090248014, US20050096589, etc. 
     Recently, the use of magnetotactic entities, used with an applied magnetic field, has also been studied for medical purposes. 
     Magnetotactic entities are defined as untethered entities where the source of propulsion or the system responsible for the displacement of the entity is part of, attached to, or embedded in the entity itself. Magnetotactic entities include a group of objects or microorganisms and any biological system or hybrid system including micro- and nano-systems or structures made of biological and/or synthetic (including chemical, artificial, etc.) materials and/or components where the directional motion can be influenced by inducing a torque from a directional magnetic field (e.g. from a permanent magnet) or electro-magnetic field (magnetic field includes here electro-magnetic field generated by an electrical current flowing in a conductor), a method referred to here as magnetotaxis where the direction of motion of such magnetotactic entities is influenced by a directional magnetic field (the magnetotactic entities can also be functionalized and be attached to other structures if required). Examples of such magnetotactic entities include but are not limited to a single or a group (swarm, agglomeration, aggregate, etc.) of flagellated Magnetotactic Bacteria (MTB), or other bacteria or other microorganisms capable of self-propulsion and influenced for the purpose of directional control by a directional magnetic field that could have been modified previously accordingly from various methods including but not limited to cultivation parameters, genetics, or attached, embedded to other entities modified to allow control by magnetotaxis such as other cells (including red blood cells), or attached to a synthetic structure that can be influenced by a directional magnetic field or gradient, or by adding micro- or nano-components to the bacteria, cells, or other microorganisms to make the directional motion of the implementation including hybrid (made of biological and synthetic components) implementation sensitive to magnetotaxis or a directional magnetic field such as the one capable of influencing the direction of a magnetic nano-compass needle. 
     U.S. Pat. No. 9,905,347, incorporated herein by reference describes a system for steering magnetotactic entities in a subject. U.S. Pat. No. 9,905,347 describes a system and method for generating a 3D-convergence point using at least three sets of magnetic field sources arranged along three axes or in three planes. However, the development of such a system that is adapted for clinical use and for a plurality of interventions relating to different ailments entails certain logistic and dimensional quandaries. This is due to space constraints, the size of the magnetic field sources and the generating of a 3D convergence point in subject that is positioned in proximity of the magnetic field sources. 
     SUMMARY 
     The present disclosure relates to a system for steering magnetotactic entities in a subject, and more particularly to the layout of the system that fits six magnetic field sources (three pairs of two magnetic heads), a platform or table for receiving a subject and an imaging device, while providing for sufficient space for allowing a physician to perform medical interventions on the subject that is resting on the table. 
     The system includes a support structure for receiving and fixing the magnetic heads in a given orientation. The support structure surrounds the table on which the subject is laid, such that the magnetic heads can generate a magnetic field for steering the magnetotactic entities in a subject to a target zone, where the steering may be done in three dimensions, where each pair of magnetic heads is aligned with a given one of three axes. 
     The pairs of magnetic heads can generate a 3D convergence point towards which the magnetotactic entities will navigate towards and converge. A three-dimensional convergence point (CP) in a magnetic field is a point, unbounded in space, to which the entities following the direction of the magnetic field in an aggregation zone (AZ) will move to and aggregate. The magnetic field at the convergence point is effectively zero and surrounding the convergence point in the aggregation zone, the effective field points from all directions to the convergence point. Because a magnetic field is not a point source, at least one of the magnetic field sources will be time-varied to cause the entities to move toward the convergence point and stay close to the convergence point. 
     Therefore, maintaining any two axes (x, y or z) with a constant (static) magnetic field and changing the direction of the other axis depending upon the other two axes being maintained constant will generate a convergence point. Similarly, maintaining one axis constant and changing the direction of the other two axes in a time-multiplexed fashion at the same time (synchronized) or with a phase shift (e.g., phase delay) will function to generate a convergence point, provided that, when the magnetotactic entity is a magnetotactic bacteria, the change is done at a frequency that allows for appropriate reaction of the magnetotactic entity, such as between 0.1 and 5 Hz or preferably about 0.5 Hz. The direction of all three axes can be changed in a time-multiplexed fashion simultaneously or with a delay between each axis. All combinations are possible provided that the magnetic field gradient of at least one axis (x, y or z) changes direction in a time-multiplexed fashion with a switching speed appropriate with the reaction time of the magnetotactic entities. 
     A broad aspect is a system for steering magnetotactic entities in a subject, the magnetotactic entities having a propulsion system for navigating in a body of the subject using a magnetic field sufficient for influencing the direction of the magnetotactic entities on the magnetotactic entities. The system includes a table for receiving a subject; three pairs of magnetic heads for generating the magnetic field for influencing a direction of the magnetotactic entities in a subject; and a support structure, surrounding the table, for supporting each of the magnetic heads of the three pairs of magnetic heads in a configuration wherein each pair is aligned along one of three axes and wherein each of the magnetic heads of each pair of the three pairs are facing one another, wherein the magnetic heads of the three pairs surround the table. 
     In some embodiments, a first magnetic head of a first pair of the three pairs may be placed under the table, joined to a portion of the support structure. 
     In some embodiments, the first magnetic head of the first pair of the three pairs may be at an angle with an axis that is orthogonal with a length of the table. 
     In some embodiments, the support structure may include a support arch for receiving a first magnetic head of a second pair of the three pairs of magnetic heads, a first magnetic head of a third pair of the three pairs of magnetic heads and a second magnetic head of the first pair of the three pairs of magnetic heads. 
     In some embodiments, the legs of the support arch may be oriented with respect to one another to create an angle of 90 degrees. 
     In some embodiments, the first magnetic head of the second pair of the three pairs of magnetic heads may be received at or near a bottom of a first leg portion of the support arch and the first magnetic head of the third pair of the three pairs of magnetic heads is received at or near a bottom of a second leg portion of the support arch. 
     In some embodiments, the support structure may include two support arms, wherein a first of the two support arms receives a second magnetic head of a second pair of the three pairs of magnetic heads and a second of the two support arms receives a second magnetic head of a third pair of the three pairs of magnetic heads. 
     In some embodiments, the first of the two support arms may receive the second magnetic head of a second pair of the three pairs of magnetic heads at or near a top of the first of the two support arms and the second of the two support arms receives a second magnetic head of a third pair of the three pairs of magnetic heads at a top of the second of the two support arms. 
     In some embodiments, the support structure may include a support arch for receiving a first magnetic head of a first pair of the three pairs of magnetic heads, a first magnetic head of a second pair of the three pairs of magnetic heads, and a first magnetic head of a third pair of the three pairs; and two support arms, wherein a first of the two support arms receives a second magnetic head of the second pair of the three pairs of magnetic heads and a second of the two support arms receives a second magnetic head of the third pair of the three pairs of magnetic heads. 
     In some embodiments, the two support arms may be each positioned on opposite sides at or near a first end of the table and the support arch is positioned at or near a second end of the table opposite the first end of the table. 
     In some embodiments, the system may include an x-ray image intensifier located between the support arch and one of the two support arms for generating imaging information of the subject. 
     In some embodiments, the system may include an actuator for displacing the table along at least one of the three axes. 
     In some embodiments, the actuator may be configured to displace the table vertically. 
     In some embodiments, the actuator may be configured to rotate the table. 
     In some embodiments, the three pairs of magnetic heads may be configured to generate a 3D convergence point that is a point, unbounded in space, to which the magnetotactic entities following a direction of the magnetic field in an aggregation zone will move to and aggregate in the body of the subject. 
     Another broad aspect is a system for steering self-propelled magnetotactic entities in a body of a subject. The system includes a first vertical support oriented in a transverse direction (y-axis) and having an upper portion in communication with a first lower portion (+y) and a second lower portion (−y); a second vertical support spaced from the first lower portion (+y) of the first vertical support in a longitudinal direction (+x); a third vertical support spaced from the second lower portion (−y) of the first vertical support in the longitudinal direction (+x) and spaced from the second vertical support in the transverse direction (y-axis); and a first pair of opposing magnetic heads arranged along a first axis, a first magnetic head of the first pair of opposing magnetic heads being affixed to the upper portion of the first vertical support and a second magnetic head of the first pair of opposing magnetic heads being affixed to a floor, the first axis forming an acute angle with respect to a plane of the floor; a second pair of opposing magnetic heads arranged along a second axis substantially orthogonal to the first axis, a first magnetic head of the second pair of opposing magnetic heads being affixed to the second lower portion (−y) of the first vertical support and a second magnetic head of the second pair of opposing magnetic heads being affixed to an upper portion of the second vertical support (+y); and a third pair of opposing magnetic heads arranged along a third axis substantially orthogonal to the first axis and the second axis, a first magnetic head of the third pair of opposing magnetic heads being affixed to the first lower portion (+y) of the first vertical support and a second magnetic head of the third pair of opposing magnetic heads being affixed to an upper portion of the third vertical support. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood by way of the following detailed description of embodiments of the invention with reference to the appended drawings, in which: 
         FIG.  1    is a drawing of a perspective view of an exemplary system for steering magnetotactic entities in accordance with the disclosed embodiments; 
         FIG.  2    is a drawing of a perspective view of the system of  FIG.  1   , without the table, showing the magnetic head that may be positioned under the table; 
         FIG.  3    is a drawing of perspective view of the system of  FIG.  1   , where a subject is laid on the table with its legs positioned for a medical intervention in the pelvis (such as rectal cancer, prostate cancer, interventions in the genital organs, etc.), and where a doctor is positioned under the exemplary support arch of the system, treating the subject; 
         FIG.  4    is a drawing of a top-down view of the system of  FIG.  1    without the imaging device; 
         FIG.  5    is a drawing of a close-up of the magnetic head of the system of  FIG.  1    that is to be located under the table of the system of  FIG.  1   ; 
         FIG.  6    is a block diagram of an exemplary system for steering magnetotactic entities; 
         FIG.  7    is an electric schematic of electrical components of an exemplary system for steering magnetotactic entities in a subject; 
         FIG.  8    is a schematic of exemplary positions of the magnetic heads with respect to one another; 
         FIG.  9    is a drawing of a front view of another exemplary system for steering magnetotactic entities in accordance with the disclosed embodiments; 
         FIG.  10    is a drawing of a front view of the exemplary system of  FIG.  9    for steering magnetotactic entities in accordance with the disclosed embodiments; and 
         FIG.  11    is a drawing of a front view of another exemplary system for steering magnetotactic entities in accordance with the disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.” 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     From the foregoing it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the teachings. Accordingly, the claims are not limited by the disclosed embodiments. 
     The present disclosure relates to a system for steering magnetotactic entities in a subject, namely for the purposes of harnessing the magnetotactic entities for therapy, imagery, diagnostics, etc. For instance, a therapeutic agent, an imagery agent and/or a diagnostic agent may be linked to the magnetotactic entities, where the entities, once introduced into the subject (e.g. by injection), are steered towards, and may converge at, a targeted zone in the body of the subject, the magnetotactic entities steered by the magnetic field. As such, the present system enables the steering of these magnetotactic entities in a subject, once they have been introduced into the subject (e.g., by injection or otherwise). The injection may occur inside the target zone (e.g. intratumoral) or around the target zone (e.g. peritumoral). 
     The target zone may include one or more hypoxic zones, such as those resulting in a tumor. The target zone may include one or more hypoxic non-vascularized regions in the body of the subject resulting from or associated with, e.g., an ischemic stroke, pulmonary hypertension, ischemic cardiopathy, diabetic retinopathy, etc. 
     The magnetotaxis system employs a magnetic field mainly for directional control of magnetotactic entities (without inducing a displacement force to the entities). The fact that the magnetic field from the magnetotaxis system is only intended for directional control or steering and not to provide a propelling or pulling force (although a small if not negligible pulling force may be present close to the magnetic head), translates into the need for a much lower magnitude (intensity) of magnetic field which makes the navigation of magnetotactic entities technologically possible using much less power. 
     The system is configured to provide sufficient space (e.g. more than 1.5 meters between the centers of each of the support arms for a human) for the subject laid out on an operating table surrounded by the magnetic sources of the system. The space provided for the subject accommodates subjects of different sizes (such as a child or a fully-grown adult), where the size can also be dictated by the weight of the subject. As different medical interventions require that the subject adopt certain positions (e.g. for pelvic examination: on the subject&#39;s back with their legs angled and in the air; for an intervention at the pancreas: on the side with legs spread apart; the supine position, etc.), the space provided to accommodate the subject is also sufficient to set the subject in these different positions such that one or more members of the medical staff (e.g. physicians, nurses, technicians, etc.) can access the subject with little to no hindrance by the structure of the magnetotaxis system. 
     Definitions 
     In the present disclosure, by “medical intervention,” it a meant a procedure performed on a subject for at least one of treatment (e.g., removal of a mass—tumor— through surgery), imaging (e.g., endoscopy, colonoscopy, optical coherence tomography, etc.) and diagnosis (which can involve one or more imaging techniques). 
     In the present disclosure, by “subject”, it is meant mammals and non-mammals. Mammals mean any member of the mammalia class including, but not limited to, humans. Non-mammals include birds, reptiles, etc. The term “subject” should not bring on any limitations as to the sex or age. Even though the configuration of the system has been determined to accommodate a human subject adopting different intervention positions as explained herein, it will be understood that the present system can be used with non-human subjects (i.e. animals), without departing from the present teachings, provided that the animal can fit within the space defined by the structure of the system and there is sufficient room for the members of the medical staff (e.g. veterinarian; technician) to access the subject and/or circulate around the subject. 
     Exemplary System for Steering Magnetotactic Entities: 
     Reference is now made to  FIG.  1   , illustrating an exemplary system  100  for steering magnetotactic entities. 
     The system  100  includes a table  105 , six magnetic heads  102  grouped in pairs, and a support structure  110  for supporting the magnetic heads  102  in a given configuration. 
     The system  100  may include an imaging device  115  such as an x-ray image intensifier such as a C-arm. 
     The magnetic heads  102  generate the magnetic field for steering the magnetotactic entities. As such, the magnetic heads  102  each have one or more magnetic coils surrounding a ferromagnetic core that generates a magnetic field when a current is passed therethrough. The magnetic heads  102  are paired together, thereby forming at least three pairs. Each of the pairs of magnetic heads  102  is defined by one axis of three axes that are orthogonal with one another. In embodiments, none of the three axes that define the orientation of the magnetic heads  102  is parallel with the floor, and none of the three axes is parallel with any of reference axes x, y and z (where the x-axis is parallel with the floor). The pairs of magnetic heads  102  may establish a point in a body of the subject where the magnetotactic entities will navigate towards and converge, using, for instance, the techniques described in U.S. Pat. No. 9,905,347. However, due to the size of the magnetic heads  102 , the requirement of providing sufficient space to fit a subject amongst the magnetic heads  102  such that the convergence point or magnetic field generated by the magnetic heads  102  can be generated in the body of the subject, and to provide sufficient space to allow a physician to access the subject when lying on the table  105  (considering that the space occupied by the subject and physician may depend on the nature of the procedure to be performed on the subject, as explained herein), a support structure may be needed. 
     Support structure  110  supports each of the magnetic heads  102  in their given configuration where the magnetic heads of each pair of magnetic heads  102  are positioned in opposition to one another along an axis oriented orthogonally with respect to the axes of the other pairs of magnetic heads  102  for generating a magnetic field capable of steering the magnetotactic entities in three dimensions. The magnetic heads  102  of each pair of magnetic heads  102  are facing one another. The support structure  110  may include a support arch  103  and two support arms  101 . 
     The support arch  103  and the two support arms  101  may be positioned at or near opposite ends of the table  105  such that the magnetic heads  102  supported thereby can be fixed in a proper orientation for generating the necessary magnetic field adapted for creating a torque along each of the three axes x, y and z. 
     Each of the support arms  101  may support one magnetic head  102  of a different pair of magnetic heads  102 . The magnetic head  102  may be positioned at or near a top of the support arm  101 . The support arm  101  may be shaped such that the support arm  101  is arched downward, or may have a vertical portion and a portion for receiving a magnetic head  102  that is at an angle with the vertical portion of the support arm  101 , thereby orienting the magnetic head  102  at least slightly downward, towards the table  105 . As such, the shape of the support  101  may be determined to position the magnetic head  102  attached thereto in a proper angle to face the corresponding other magnetic head  102  of the pair of magnetic heads  102 . The orientation of the magnetic head  102  may be such that the magnetic head  102  supported by the support arm  101  is facing the corresponding magnetic head  102  of the magnetic head pair, as described herein. In some embodiments, each of the support arms  101  may be connected to one another at a base portion (e.g. joins the base of the table  105 .) In other embodiments, each of the support arms  101  may be separate from the table  105 . 
     In some examples, the support arms  101  may be configured to move away and towards the table  105 , e.g. in order to create additional space for placing the patient on the table  105 . For instance, the support arms  101  may be positioned on rails, where the support arms  101  may slide along the rails to create additional space. 
     In some examples, the magnetic heads  102  may be pivotably attached to the support arms  101  or the support arch  103 , such that they may be displaced in order to further create space between the magnetic heads  102 , e.g. for placing the patient on the table  105 . 
     The support arch  103  may support one or more magnetic heads  102 . As is shown in the example of  FIG.  1   , the support arch  103  supports three magnetic heads  102 . A first magnetic head  102  supported by the support arch  103  is paired with a magnetic head  102  supported by the first support arm  101 , a second magnetic head  102  supported by the support arch  103  is paired with a magnetic head  102  supported by a second support arm  102 , and a third magnetic head  102  supported by the supper arch  103 , centered on the support arch  103 , is paired with the magnetic head  102  positioned under the table  105 . 
     The support arch  103  has two leg portions, contacting the ground and that are substantially vertical (the leg portion may have a slight curve or bend as illustrated, for instance, in  FIG.  1   ) and an arch portion that is curved, interconnecting the two leg portions of the support arch  103 . 
     Each of the leg portions of the support arch  103  may receive one magnetic head  102 . The magnetic head  102  may be located near or at the bottom of the leg portion of the support arch  103 . The width or thickness of the leg portion of the support arch  103  may be greater towards the bottom in order to support the magnetic head  102  (e.g. may not be uniform). In some examples, the leg portion of the support arch  103  may include a user input interface for controlling the system (e.g. the generating of a magnetic field using the pairs of magnetic heads  102 ). 
     The arch portion of the support arch  103  creates a space as a result of the elevation of the middle of the arch for an intervening physician to access the subject, as shown in  FIG.  3   . 
     In some examples, instead of a pair of support arms  101 , the system  100  may include a second support arch for receiving the two magnetic heads  102  instead of the support arms  101  (not shown). 
     It will be understood that the orientation and position of the magnetic heads  102  shown in  FIGS.  1 - 5    illustrate one example of same that was developed for meeting the size constraints and to generate sufficient space for the subject and intervening members of medical staff to perform certain medical interventions, as described herein, where certain medical interventions require that the subject be laid in a given position. 
     The table  105  is adapted to receive the subject into whom will be introduced the magnetotactic entities. As such, the length of the table  105  may be sufficient to receive one of possible subjects of different heights and widths lying down (e.g. over 6.5 feet). The table  105  may be adapted to move back-and-forth, side-to-side and/or up-and-down (i.e. along one or more of the three axes x, y, and z). In some embodiments, the table  105  may also be configured to rotate clockwise and/or counter-clockwise. The movement of the table  105  may be controlled by a user using a user input interface, such as the one appearing on the leg portion of the support arch  103  in  FIG.  1   . In other embodiments, the system  100  may be controlled remotely (e.g. using a remote control that communicates wirelessly with the system  100 ; a computing device such as a tablet computer or smartphone including program code for controlling the system  100  when executed by the processor of the computing device, etc.) 
     The table  105  may be layered with a thin mattress or cushion to provide comfort for the subject. In some examples, the table  105  may have extensions for receiving the arms of the subject. 
     The imaging device  115  is configured to obtain information on the anatomy of the subject (imaging of the inside of the subject). In some embodiments, this information may be used to monitor the progress of the magnetotactic entities in the subject, determine the location of the target site towards which the magnetotactic entities will be steered, to provide visuals for the purpose of a medical intervention such as a surgery, etc. The imaging device  115  may be an X-ray image intensifier, such as a C-arm. However, it will be understood that other imaging devices may be used without departing from the present teachings. 
     In some examples, as shown in  FIG.  1   , the imaging device  115  may fit in a space between the support arm  101  and the support arch  103 . When the imaging device  115  is a C-arm, the arch of the C-arm may arch around the table  105  such that the C-arm can gather information on the subject lying on the table  105 , where, e.g., the table  105  may move up and down with respect to the C-arm such that the C-arm can provide imaging data along a length of a body of the subject. In some embodiments, the imaging device  115  may be displaced manually or remotely, having, for instance, a pair of wheels for rolling the imaging device  115  into different positions. 
       FIG.  11    illustrates another exemplary design of the system  100  of  FIG.  1   . 
     Reference will now be made to  FIG.  3    to further illustrate an exemplary system for steering magnetotactic entities as described herein. The layout of the system  100  may be dictated by the size of the magnetic heads  102 , the positioning on the surface to receive a subject such that the pairs of magnetic heads  102  may generate a magnetic field for steering magnetotactic entities introduced into the subject, and finally to allow a physician to have access to the subject in order to conduct a medical intervention. 
     In some embodiments, the dimensions of the support arch  103 , the orientation of the leg portions of the support arch  103  and the orientation of the magnetic heads  102  fixed thereon are to allow access to a physician to fit within the space defined by the arch  103 . Moreover, for certain medical procedures, the position of the subject may result in the subject occupying more space. For instance, for a medical intervention pertaining to rectal cancer, the subject&#39;s legs are suspended and spread open as illustrated in  FIG.  3   . As such, the layout of the system  100  takes into account the space occupied by the subject and the physician during different medical procedures, and more particularly with respect to those where the subject occupies a greater amount of space due to the position of the subject. The magnetic head  102  positioned at the top of the support arch  103  faces towards the table  105 , and mirroring the orientation of the magnetic head  102  positioned under the table  102 . By having the magnetic head  102  positioned at the center of the support arch  103  be oriented towards the table  105 , thereby not being entirely vertical, this provides sufficient space far a seated physician to be positioned under the support arch  103 , the angled magnetic head  102  providing more space under the support arch  103 . 
     The leg portions of the support arch  103  are not parallel, e.g. may define an angle of 90 degrees or less with respect to one another. 
     In some examples, for treating breast cancer, the system  100  is adapted to generate a target zone near or at the breast while the subject is lying on the table  105 . This may be further achieved by having the table  105  move up and/or down in order to reposition the subject with respect to the magnetic heads  102 . 
     Reference is made to Table 1, illustrating an exemplary list of possible positions of a human subject associated with different body parts that are subject to medical interventions that may be performed on the subject. The configuration of the system  100  (e.g. the space surrounding the table  105 ) is to provide sufficient space for the subject laid in one of those positions, and for the members of the medical staff to carry out the necessary interventions. The space may also be for accommodating the subject as the subject is shifted between positions during the medical intervention: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 list of exemplary parts of a human subject&#39;s body that can be subject 
               
               
                 to a medical intervention and that were taken in account in the layout 
               
               
                 of an exemplary system for steering magnetotactic entities. 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                   
                 Position of 
                   
                 Additional 
               
               
                   
                   
                   
                 the 
                   
                 information to 
               
               
                   
                 Exemplary 
                 Position of 
                 member of 
                 Possible 
                 consider for 
               
               
                 Location 
                 possible targets 
                 the subject 
                 the medical 
                 instruments 
                 space 
               
               
                 of body 
                 in the subject 
                 on the table 
                 staff 
                 used 
                 requirements 
               
               
                   
               
               
                 Head and 
                 Tongue, larynx, 
                 Laying on 
                 Standing 
                 Ultrasound 
                 The member of 
               
               
                 neck 
                 throat, salivary 
                 back with 
                 next to head 
                 device, suction 
                 medical staff 
               
               
                   
                 glands, 
                 immobilized 
                 of subject 
                 device, 
                 may have to 
               
               
                   
                 oesophagus, ear 
                 head 
                   
                 injection 
                 turn around the 
               
               
                   
                   
                   
                   
                 syringe 
                 head of the 
               
               
                   
                   
                   
                   
                   
                 subject 
               
               
                 Pelvis 
                 Anus, rectum 
                 Laying on 
                 Sitting and 
                 Ultrasound 
                 The subject&#39;s 
               
               
                   
                   
                 back, legs 
                 facing the 
                 device, 
                 legs may be 
               
               
                   
                   
                 spread in the 
                 subject&#39;s 
                 rectoscope, 
                 moved to a 
               
               
                   
                   
                 air 
                 pelvis 
                 injection 
                 horizontal and 
               
               
                   
                   
                   
                   
                 syringe, 
                 parallel 
               
               
                   
                   
                   
                   
                 stabilizer 
                 position during 
               
               
                   
                   
                   
                   
                 balloon 
                 an intervention 
               
               
                 Pancreas 
                 Pancreas 
                 Laying on 
                 Sitting next 
                 A device for 
                 The pancreas 
               
               
                   
                   
                 back, legs 
                 to upper 
                 both 
                 provides for 
               
               
                   
                   
                 spread in the 
                 part of the 
                 ultrasound and 
                 difficult access 
               
               
                   
                   
                 air 
                 subject&#39;s 
                 endoscopy, 
                 being behind 
               
               
                   
                   
                   
                 body with a 
                 injection 
                 the stomach 
               
               
                   
                   
                   
                 nurse 
                 syringe, 
               
               
                   
                   
                   
                 positioned 
                 catheter 
               
               
                   
                   
                   
                 next to the 
               
               
                   
                   
                   
                 bottom part 
               
               
                   
                   
                   
                 of the 
               
               
                   
                   
                   
                 subject&#39;s 
               
               
                   
                   
                   
                 body 
               
               
                 Breast 
                 Breast 
                 Laying on 
                 Standing 
                 Ultrasound, 
                 The breast may 
               
               
                   
                   
                 back, body 
                 next to the 
                 injection 
                 have to be 
               
               
                   
                   
                 can shift 
                 subject 
                 syringe, 
                 significantly 
               
               
                   
                   
                 from left to 
                   
                 catheter 
                 manipulated by 
               
               
                   
                   
                 right of the 
                   
                   
                 the physician 
               
               
                   
                   
                 table, where 
                   
                   
                 during the 
               
               
                   
                   
                 the body may 
                   
                   
                 intervention 
               
               
                   
                   
                 not be in the 
                   
                   
                 due to the 
               
               
                   
                   
                 middle of the 
                   
                   
                 mobility of the 
               
               
                   
                   
                 table 
                   
                   
                 breast 
               
               
                 Colon 
                 Caecum, 
                 Laying on 
                 Standing 
                 Colonoscope, 
                 Due to the size 
               
               
                   
                 ascending colon, 
                 side or on the 
                 and facing 
                 injection 
                 of the colon, the 
               
               
                   
                 descending 
                 back 
                 the back of 
                 syringe 
                 position of the 
               
               
                   
                 colon, transversal 
                   
                 subject 
                   
                 subject 
               
               
                   
                 colon, sigmoid 
                   
                 (when 
                   
                 depending on 
               
               
                   
                 colon 
                   
                 subject is 
                   
                 the point of 
               
               
                   
                   
                   
                 lying on 
                   
                 intervention 
               
               
                   
                   
                   
                 their side) 
                   
                 may vary 
               
               
                   
               
            
           
         
       
     
     As illustrated by the examples of Table 1, depending on the nature of the intervention, the subject and the intervening members of the medical staff take up varying amounts of space. The layout of the system is configured to provide for the space occupied by the members of the medical staff. This is because the system  100  can be used to prepare for, and/or for use with, many possible medical interventions. 
     In an exemplary embodiment, the distance between the first and second support arms  101 , measured from their respective centers at their base, may be of 1698 mm. The table  105  may be position at the midpoint between the first and second support arms  101 . An exemplary support arch  103  may have a height of 2540 mm, a width of 1593 mm measured from the respective centers of the base of the leg portions of the support arch  103 . It will be understood that other possible dimensions may be possible without departing from the present teachings. 
     Exemplary Computer Architecture of an Exemplary System for Controlling Magnetotactic Entities: 
     Reference is now made to  FIG.  6   , illustrating an exemplary computer architecture of an exemplary system for controlling magnetotactic entities  100 , interacting with certain of the components of the system  100 . 
     The system  100  includes a processor  201 , memory  203  (e.g. on a printed circuit board—PCB) and a controller  205  (e.g. including a current amplifier). 
     The system  100  may include a user input interface  202  and/or a display  204 . The computer may include an actuator  206 . 
     The processor  201  may be a programmable processor. In this example, the processor  201  is shown as being unitary, but the processor may also be multicore, or distributed (e.g. a multi-processor). 
     The computer readable memory  203  stores program instructions and data used by the processor  201 . The memory  203  may include non-transitory storage to store the program instructions. The computer readable memory  203 , though shown as unitary for simplicity in the present example, may comprise multiple memory modules and/or caching. In particular, it may comprise several layers of memory such as a hard drive, external drive (e.g. SD card storage) or the like and a random access memory (RAM) module. The RAM module may store data and/or program code currently being, recently being, or soon to be processed by the processor  201  as well as cache data and/or program code retrieved from non-transitory memory, e.g., a hard drive. A hard drive may store program code and be accessed to retrieve such code for execution by the processor  201  and may be accessed by the processor  201  to store magnetic head  102  sequences for generating a convergence point for the magnetotactic entities, and imaging data from the imaging device  115 , as explained herein. The memory  203  may have a recycling architecture for storing, for instance, imaging data from the imaging device  115 , coordinates for steering the magnetotactic entities, etc., where older data files are deleted when the memory  203  is full or near being full, or after the older data files have been stored in memory  203  for a certain time. 
     The user input interface  202  is in communication with the processor  201 . The user input interface  202  allows for a user to provide input to the system  100 , e.g., for controlling the magnetic heads  102 , moving the table  105 , activating the imaging device  115 . The user input interface  202  may be one or more of a touchscreen, one or more knobs, a keyboard, a mouse, a joystick, etc. As shown in  FIG.  1   , the user input interface  202  may be integrated to a leg portion of the support arch  103  (however, the user input interface  202  may be separate from the support arch  103  or support structure  110 , or may be integrated, e.g., to a support arm  101 ). 
     The processor  201 , the memory  203  and the user input interface  202  may be linked via BUS connections. 
     The display  204  provides visual information to the user of the system  100 , such as imaging data generated by the imaging device  115 , values for the strength of the magnetic field generated by one or more pairs of magnetic heads  102 , the location of the convergence point for steering the magnetotactic entities, overlaid, e.g., over an image of the subject generated by, for instance, the imaging device  115 . The display  204  may also provide a graphical user interface for the user for controlling the system  100 . The display  204  may also include a functionality of a user input interface  202 , being configured as a touchscreen. 
     The one or more actuators  206  controls the position of the table  105 . The one or more actuators  206 , upon receiving commands from the processor  201 , may cause the table to move up-or-down, side-to-side, forwards-or-backwards, or rotate. The one or more actuators  206  may be any combination of pneumatic, hydraulic, supercoiled, electric, rotary, linear, etc. 
     One or more controllers  205  (e.g. including current amplifiers) may be present for controlling the flow of current to the one or more magnetic heads  102 , in order to cause the generation, or modifying the generation of the magnetic field generated by the one or more magnetic heads  102  when powered, as described in further detail below. 
     The user may control the system  100  by providing input via the user input interface  202 . For instance, the user may provide input for activating one or more of the magnetic head pairs (or this may be done implicitly by the user designating a target in the subject). The processor  201  receives the input for turning on one or more of the magnetic heads, and sends commands to cause the controller  205  to open one or more switches and/or modulate current being directed to the one or more magnetic head pairs (e.g. through current amplifiers), as described in further detail below. In some embodiments, where the user provides a target for steering the magnetotactic entities, the processor  201  may retrieve from memory  203  one or more commands or functions to identify the appropriate magnetic head pairs  102  to turn on, the appropriate current to be provided to the one or more magnetic heads, and/or if the current is to remain constant, and/or if the magnetic field generated by each of the magnetic heads  102  is to remain constant or is to fluctuate in a time multiplexed manner, as explained in U.S. Pat. No. 9,905,347. In some embodiments, upon the user selecting a target in a subject for the steering of the magnetotactic entities, the processor  201  may also generate one or more commands transmitted to the actuator  206  in order to displace the table  105 , and the user positioned thereon, for positioning the subject with respect to the convergence point that may be generated by the pairs of magnetic heads  102 . 
     The user may also provide input via the user input interface  202  to displace the table  105 . This input is received by the processor  201 , where the processor  201  retrieves from memory  203  commands or functions to calculate table adjustment(s) and sends commands corresponding to the user input to the actuator  206  to cause the table  105  to be displaced. 
     The user input interface  202 , processor  201  and memory  203  may be used to control the imaging device  115 . However, in some embodiments, the imaging device  115  may have a separate computer, including a user input interface, for interacting with same. 
       FIG.  7    depicts a controller  205  in communication with the components of a magnetic head subsystem  700 . As explained above, the controller  205  is in communication with the processor  201  (see  FIG.  6   ). The processor  201  sends commands to the controller  205  and may receive various types of data from the controller  205  relating to the state of the components of the magnetic head subsystem. The controller  205  controls the components of the magnetic head subsystem  700  to provide drive signals to the magnetic heads  102 . 
     The magnetic heads  102  may be configured as three pairs of opposing heads, each pair aligned along one of three orthogonal axes. For example, a first pair of opposing magnetic heads ( 710 A,  710 B) may be positioned along a first axis, a second pair of opposing magnetic heads ( 715 A,  715 B) may be aligned along a second axis, and a third pair of opposing magnetic heads ( 720 A,  720 B) may be aligned along a third axis. 
     The magnetic head subsystem  700  includes a source  705 , e.g., a radio frequency oscillator, to provide current to the magnetic heads  102 . The output of the source  705  may be fed to a number of drive component chains, each of which may include a modulator/switch ( 720 A,  720 B,  720 C), a phase shifter ( 725 A,  725 B,  725 C), and a drive ( 730 A,  730 B,  730 C). In disclosed embodiments, there may be a separate source  705  for one or more of the drive component chains, e.g., a separate source for each drive component chain. 
     In the example depicted, each pair of magnetic heads (e.g.,  710 A,  715 A) has an associated chain of drive components (e.g.,  720 A,  725 A,  730 A). In disclosed embodiments, a full chain of drive components may be provided for only a subset of the pairs of magnetic heads. For example, if only two of the three pairs of magnetic heads are to receive modulated signals, then the drive (e.g.,  730 C) of the third pair of magnetic heads (e.g.,  710 C,  715 C) could be in communication with the source  705  without an intervening modulator/switch (e.g.,  720 C). Similarly, in disclosed embodiments, the phase shifter (e.g.,  725 C) may be omitted from a respective drive component chain if the corresponding pair of magnetic heads (e.g.,  710 C,  715 C) does not require a phase-shifted signal at the input of the drive (e.g.,  730 C). 
     The modulator/switch ( 720 A,  720 B,  720 C) receives the output of the source  705  and performs modulation or switching to generate a desired waveform, e.g., a square-wave or pulsed waveform. One of ordinary skill in the art would understand that a modulator can be implemented with various circuit architectures, including in a form that is, in essence, a switch. Hence, the terms “modulator/switch,” “modulator,” and “switch” are used interchangeably in the present specification, including the claims. The output of the modulator/switch ( 720 A,  720 B,  720 C) is received by a phase shifter ( 725 A,  725 B,  725 C), which applies a determined phase shift to the drive signal, e.g., by applying a delay to the signal. In this example, the phase shifter ( 725 A,  725 B,  725 C) is depicted as a separate component. However, one of ordinary skill in the art would understand that a phase shift could instead be provided by another component, such as the modulator/switch. 
     Each drive component chain includes a drive (e.g.,  730 A) which outputs a drive current to a pair of the magnetic heads (e.g.,  710 A,  715 A). The drive (e.g.,  730 A) receives a drive signal from the source  705 —possibly after passing through a modulator/switch (e.g.,  720 A) and/or a phase shifter (e.g.,  725 A). The drive ( 730 A,  730 B,  730 C) may be, for example, an amplifier which amplifies a received drive signal to generate a high power drive current (or voltage) to drive a pair of the magnetic heads. In disclosed embodiments, the drive (e.g.,  730 A) may output drive currents of opposite polarity to respective ones of the pair of magnetic heads (e.g.,  710 A,  715 A). One of ordinary skill in the art would understand that a separate drive may be used for each magnetic head. 
       FIG.  8    depicts a geometric relationship of positions and orientations of the magnetic heads. As discussed above, the system  100  may include three pairs of magnetic heads ( 710 A-C,  715 A-C). The magnetic heads  102  of each pair of magnetic heads may be positioned opposed to each other (i.e., facing each other) along a particular one of three substantially orthogonal axes. By the term “substantially orthogonal” it is meant that the axes need not be precisely orthogonal—the system  100  can be calibrated for axes which vary somewhat (e.g., +/−5% or +/−10%) from orthogonality. 
     The magnetic heads ( 710 A-C,  715 A-C) are held in position by the support arms  101  or the support arch  103  or positioned on the floor, i.e., under the table  105  (see  FIG.  1   ). In the example depicted, a first pair of magnetic heads ( 710 A,  715 A) is positioned such that a first magnetic head  710 A is affixed to the support arch  103 , while the second, opposing magnetic head  715 A is affixed to the floor or to a base in contact with the floor. A second pair of magnetic heads ( 710 B,  715 B) is positioned such that a first magnetic head  710 B is affixed to the lower portion of one of the legs of the support arch  103 , while the second, opposing magnetic head  715 B is affixed to one of the support arms  101 . Similarly, a third pair of magnetic heads ( 710 C,  715 C) is positioned such that a first magnetic head  710 C is affixed to the lower portion of the other leg of the support arch  103 , while the second, opposing magnetic head  715 C is affixed to the other support arm  101 . 
     As a reference, a set of orthogonal axes may be defined relative to the plane of the floor, with the x-axis running along the floor in a direction away from the support arch  103  and toward a mid-point between the support arms  101 , i.e., from the head to the foot of the table  105  (see  FIG.  1   ), the y-axis running along the floor in a direction perpendicular to the x-axis, and the z-axis running in a vertical direction toward the ceiling. In the example depicted, none of the first, second, or third axes of the pairs of magnetic heads ( 710 A-C,  715 A-C) is orthogonal to the x, y, or z axes. 
     Specifically, the second magnetic head  715 A of the first pair of magnetic heads ( 710 A,  715 B) is positioned to form an angle, α, with respect to the x-axis (i.e., with respect to the plane of the floor), where a is less than 90°. In some examples, a may be 54 degrees. As such, the axis of the first pair of magnetic heads ( 710 A,  715 A) forms an angle of 90°-α with the z-axis (i.e., the vertical axis). The axis of the second pair of magnetic heads ( 710 B,  715 B) extends from one of the support arms  101  to the lower portion of a leg of the support arch  103  and, thus, is not parallel to the x or y axes (or the z-axis) and, consequently, is not parallel or perpendicular to the table  105  (see  FIG.  1   ). In some embodiments, θ may be around 25 degrees (e.g. 23.9 degrees). Similarly, the axis of the third pair of magnetic heads ( 710 C,  715 C) extends from the other support arm  101  to the lower portion of the other leg of the support arch  103  and, thus, is not parallel to the x or y axes (or the z-axis) and, consequently, is not parallel or perpendicular to the table  105  (see  FIG.  1   ). In some embodiments, β may be equal to θ (e.g. around 25 degrees, such as 23.9 degrees). 
     By virtue of the geometric relationship described above, it can be seen that the first magnetic head  710 A of the first pair of magnetic heads ( 710 A,  715 A) is not directly over the center of the table  105  (see  FIG.  1   ) where it would interfere with positioning of a subject on the table  105 . Furthermore, the arrangement of the second pair of magnetic heads ( 710 B,  715 B) and third pair of magnetic heads ( 710 C,  715 C) is such that they are not positioned at the head or the foot of the table  105  (see  FIG.  1   ) where they would interfere with access to the subject by a physician. Moreover, the second pair of magnetic heads ( 710 B,  715 B) and third pair of magnetic heads ( 710 C,  715 C) are displaced vertically (i.e., above or below) relative to the level of the table  105  (see  FIG.  1   ). The geometric relationship also allows for three of the six magnetic heads to be mounted on the support arch  103  and two of the magnetic heads to be mounted on two respective support arms  101 , which reduces the complexity of the support structure. 
     In some embodiments, as shown in  FIGS.  9  and  10   , the floor, ceiling and/or walls of the room in which the system  100  is located may be used to support one or more of the magnetic heads, where the magnetic heads are positioned with respect to one another in a similar manner as described in  FIG.  8   . As such, as shown in  FIG.  9   , as one of the magnetic heads is joined to the ceiling, and two of the magnetic heads are joined to the floor, the exemplary system  100  of  FIG.  9    does not include the arch for providing support to these three magnetic heads, as the ceiling and floor replace the arch for providing support.  FIG.  10    shows the three magnetic heads of  FIG.  9    that were joined to an arch in  FIG.  1   , where two of the three magnetic heads are joined to the floor, and one of the three magnetic heads is joined to the ceiling. Necessary wiring for the system, including the magnetic heads, may respectively be passed on or under the floor, and on or in the ceiling. Similarly, in some examples, walls may also be used to support the magnetic heads that were joined to the support arms in  FIG.  1   , thereby replacing the support arms as mechanisms for supporting the magnetic heads (not shown). 
     Although the invention has been described with reference to preferred embodiments, it is to be understood that modifications may be resorted to as will be apparent to those skilled in the art. Such modifications and variations are to be considered within the purview and scope of the present invention. 
     Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawing. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings. 
     Moreover, combinations of features and steps disclosed in the above detailed description, as well as in the experimental examples, may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.