1. Field of the Invention
This invention relates to medical devices, and more particularly to magnetically guided freely moving medical devices deployed to move within the lumens, cavities and chambers of the human body.
2. Description of the Related Art
Ingestible diagnostic, delivery and therapeutic devices, such as ‘GI capsules’, traveling through the cavities and ducts of the gastrointestinal tract, have been in use since year 2001. When the patient swallows such pill, the natural muscular (peristaltic) movement of the digestive tract propels it through the intestine lumen. While the capsule is moving through the intestine lumen, a small camera enables the physician to inspect the walls of the intestinal ducts for possible detection of tumors, ulcers or bleeding. However, the speed, position and the direction of the capsule and the small camera within the capsule are uncontrolled. Obtaining and maintaining a desired observational point or viewing direction are impractical, and most of the intestinal walls remain uninspected during a single passage. Returning and delivering drugs to a specific locale is imprecise and mostly unattainable.
Manually operated devices of endoscopy and colonoscopy have limited success to reach clinically important anatomic sites, and generally do not enjoy patients' acceptance. With the rapid increase of cases of stomach ulcers and colon cancers, effective and painless methods of regular preventive and investigative examinations are needed. The supermagnetic propulsion vessel of this disclosure offers a non-contacting, controlled procedure eliminating the control instability issues associated with magnetically operated un-tethered device navigation, and enables rapid anatomic site acquisitions for location-specific diagnoses and treatments.
Therapeutic drug delivery to organs, such as the brain, the heart, the kidneys and other critical organs have similar difficulties in reaching the sites of diagnosis and therapeutic interest. Freely moving delivery capsules for deployment through the urinary ducts or the cardiovascular lumens become possible by using the supermagnetic propulsion vessel which can be levitated-suspended, moved or held in place by non-contacting external magnetic fields.
In one embodiment, as embodied and broadly described herein, a device is disclosed that is adapted to be magnetically guided due to superconductive material exhibiting supermagnetic properties. The superconductive material is contained within a thermally insulated vessel and the device can be .maneuvered using supermagnetic propulsion in response to externally generated magnetic fields. The superconductive material is advantageously positioned within the thermally insulated vessel and can be in the form of a ring, disk, plate, or other shape. Moving and directing the device is accomplished by utilizing the superconductive Meissner-effect which repels these elements in response to externally generated magnetic fields. Generating the external fields with the proper direction and magnitude relative to these supermagnetic elements, will levitate, suspend, move and orient the vessel in a stable and controllable manner. Holding the vessel in place is achieved by controlling the external magnetic fields such that the repulsive Meissner diamagnetic forces balance on the superconductive material against the weight of the device and against the various forces holding or affecting the device within the patient. Moving and directing the capsule is accomplished by electronically shaping and moving the externally generated magnetic field in relation to the capsule utilizing a variety of core-coil electromagnets suitable to produce such variable fields.
In another embodiment of the invention, the device comprises electronic equipment, such as but not limited to, a camera to take pictures and/or record video of its surroundings as well as a wireless transmitter to transmit the captured pictures and/or recorded video to an external receiver. The device further comprises a light source to illuminate the environment.
In yet another embodiment of the invention, the device comprises medical equipment, such as but not limited to, an injection or spray mechanism to administer a drug or reactive agent, or diagnostic equipment adapted to collect a sample of its environment.
These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings which illustrate by way of example the features of the invention.
Embodiments of the invention provide an improved medical device adapted to be magnetically guided within the lumens, cavities and chambers of the human body. Referring to
In an embodiment incorporating features of the invention, the vessel 102 comprises superconductive material 107, wherein the superconductive material 107 comprises at least one of superconductive rings, disks, plates, domes or a combination thereof, such that the superconductive materials 107 have supermagnetic properties. The shape of the superconductive materials 107 is not limited to the shapes listed, but can be any shape. In superconducting materials, the characteristics of superconductivity appear when the temperature of the material is lowered below the critical temperature. In an embodiment of the invention, the superconductive materials 107 are cryogenically cooled in order to attain superconductivity and to freeze the trapped magnetic fields into the superconductor. However, other cooling methods known in the art may be used to lower the temperature of the superconductive materials 107 below the critical temperature. The superconductive materials 107 can be made of anisotropic High Temperature Superconductor (HTS) materials, such as yttrium barium copper oxide (YBCO) or other superconductor materials known in the art.
The insulation material 103 provides heat transfer insulation to the capsule 100 such that the temperature increase of the superconductive materials 107 from a pre-cooled temperature to the critical temperature takes a few hours. During this time, the capsule 100 will exhibit the supermagnetic effects and will continue to be magnetically guided. In one embodiment of the invention, the insulation material 103 provides sufficient heat transfer insulation such that the capsule 100 retains superconducting characteristics for at least fifteen (15 ) minutes. In yet another embodiment, the insulation material 103 provides sufficient heat transfer insulation such that the capsule 100 retains superconducting characteristics for at least thirty (30 ) minutes. When the capsule 100 no longer exhibits superconducting characteristics, the natural peristaltic movements will excrete the capsule 100 in due time.
In embodiments of the invention, the insulation material 103 is configured to comprise a plurality of insulation layers, such as but not limited to, a plurality of Mylar® layers covered by aluminum mirror layers. However, other very low thermal-conductivity insulation layers known in the art can be used instead of Mylar® for the insulation material 103. Referring to
The capsules described herein are adapted to be magnetically guided due to superconductive materials exhibiting supermagnetic properties. The superconductive materials are contained within the thermally insulated vessel and the capsule can be maneuvered using supermagnetic propulsion in response to externally generated magnetic fields. The superconductive materials respond to externally generated magnetic fields by repelling from the externally generated magnetic fields due to the phenomenon called Meissner-effect. Generating the external magnetic fields with the proper direction and magnitude relative to these superconductive materials, will levitate, suspend, move and orient the capsule in a stable and controllable manner. Holding the capsule in place is achieved by controlling the external magnetic fields such that the repulsive Meissner diamagnetic forces balance on the superconductive material against the weight of the capsule and against the various forces holding or affecting the capsule within the body. Moving and directing the capsule is accomplished by electronically shaping and moving the magnetic loci of the externally generated magnetic fields in relation to the capsule's superconductive characteristics utilizing a variety of core-coil electromagnets suitable to produce such variable magnetic fields. In some embodiments, moving and directing the capsule is accomplished by utilizing the permanent magnet effect of trapped magnetic fields frozen into the superconductive disks, while the superconductive plates allow for axial rotation of the capsule.
In an embodiment of the capsule which has a video camera, the video signal is displayed on display 701 for the operator for man-in-the-loop navigation. The content of the video can be deciphered by image processing and the information used for navigation.
Using the capsule in any of the listed medical procedures requires the patient lying on the table 720 which is surrounded by the external magnetic field generator 730. The pre-cooled insulated vessel will be inserted, by an appropriately automated device, into a room temperature capsule, which in turn will be sealed by the same automated device. The capsule will be swallowed or inserted into the patient. The external magnetic field generator 730, regulator 703 and amplifiers 704 will be activated and the capsule navigation can begin. Sensors 710 indicate the location of the capsule and the externally generated magnetic field and field gradients begin to hold and control the capsule. An operator using input device 702, such as but not limited to a joystick, can direct the capsule as directed by the input device 702.
In one procedure of intestinal investigation each patient has on the average two hours to be examined. This means that in a regular 8 hour work day, 4 procedures can be performed using 4 capsules per day. In one embodiment, using HTS material with critical temperatures at liquid Nitrogen (77K), each table 720 comprises a cryogenic-cooler (not shown) adapted to house a plurality of vessel assemblies. In some embodiments, the cryogenic-cooler needs to keep 4 vessel assemblies at the pre-cooled temperature of approximately 55K for daily use. If the warming up temperature gradient from 55K to 77K is approximately 5K/hour, and the cool-down roughly is also 5K/hour from room temp to the pre-cooled temperature level, it will take approximately 60 hours to get a fully insulated vessel assembly ready to be deployed starting the procedure at 55K. This is approximately 2.5 days for each vessel. Thus, the cryogenic-cooler has to store a minimum of four rows of 4 vessel assemblies, the first row of 4 is ready in the morning of the first day, each vessel sitting at 55K. The fourth row of 4 is loaded in at room temperature and starts to cool down. The third and second rows of 4 and 4 are cooling down with temperatures between room and the critical temperature. Once the first row is empty, the cryogenic-cooler is adapted to rotate the rows. Thus, the minimum number of vessels in the cryogenic-cooler is 16. However, in other embodiments the cryogenic-cooler can be configured to house 5 or more vessels per row depending on factors, such as the patient throughput and/or the length of the workday. This method of revolving vessel-columns cooling down in sequence supplies continuous vessel flow available for every day. There are no electronics or any other power dissipation in the vessels during cool-down.
A number of electromagnetic coil-core configurations are suitable to generate magnetic fields with the necessary field strength and gradient. Electromagnetic coils 301, 305, 306 and 309 are configured around the patient's body having an operating or control region within the human body. To obtain the desired location and orientation of the vessel with 6 degrees of freedom, the fields are generated by independently controlling the coil current magnitudes and polarity from the amplifiers 704.
An important feature of the system of
The physics principle underlying the magnetic guidance of the medical device is a unique form of diamagnetism observed in High Temperature Superconductors (HTS) under moderate magnetic field conditions.
where H is the magnetic field, ε is the penetration depth and r is the location in a coordinate system in which E0 is the sum of the electrons energy in condensed state and the kinetic energy of the permanent super-currents. The penetration depth, named after F. & H. London, is:
where ns=n, the total number of conduction electrons in cubic centimeter. The field configuration in the interior of the HTS, which minimizes the free energy will satisfy the conditions of:
H+[εL2∇×Δ×H]=0
When combined with the Maxwell equations:
the field distribution and the currents can be calculated. Here js is the current density in the HTS. The finite solution leads to conclude that the fields will run parallel with the HTS surface and the exerted force will be determined by the field gradient across the external surface of the HTS penetrating into the material with the London depth of:
integrated over the entire surface of the HTS. The repelling force exerted on the total HTS surface is:
I is the coil current and B is the field strength generated by the external magnetic field generators at the capsule location, and the integration is over the s surface of the HTS in the capsule.
Practical computations in FEA magnetic simulations for any shapes of HTS surface can proceed based on estimating permeability less than 1.00 for accounting for the HTS Diamagnetic nature. Values of μ≦ 1/1000 produce force calculation errors less than 1%.
Force magnitude of maximum 1 Newton is obtained for a vessel volume of 4.5 mm diameter and 8 mm length. This magnitude is sufficient for controlling capsules, and micro-devices within the human body. However, the vessel walls can be very thin due to the small London penetration depth. Thus, the capsule can be very light. This is an important feature when the medical device needs to carry the useful load of diagnostic and therapeutic equipments. The limitation for larger forces is the maximum Hc critical field strength around the HTS, above which the material may be come normal even below Tc critical superconductive temperature. All calculations and simulations keep the maximum field strength below 2.5-3.0 kGauss.
The diamagnetic nature of the HTS materials used in this invention assures that the capsule movement is always along the decaying slope of the field gradient independent of the field vector polarity. The capsule can be levitated in ‘+Z’ direction and moved in the ‘X’ and ‘Y’ directions in a stable manner away from higher absolute value magnetic fields toward the lower absolute values as shown in
Using Ansoft magnetic simulation with μ=0.001, the resulting F(z) force levitating and moving the capsule upward is 1.0263 Newton (803). It is evident from
Having established the field polarity immunity in
B(z) 820 is decreasing with the same slope along the Z axis as B(x) 821 is increasing along the X axis. Again, at the capsule, the fluxes are expelled producing the gradients across the superconductive vessel with the commensurate forces driving the capsule upward as well as sideways. This case should suffice to demonstrate the concepts and the generalization for 3D control various combinations of field slopes and gradient directions.
The invention is described herein with reference to certain embodiments, but it is understood that the invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. For example, the embodiments herein disclose that the superconductive material is to be cooled below the critical temperature to attain superconductive characteristics. However, alternate superconducting materials, such as room temperature superconductive material if available, would work equally well, as long as the magnetic phenomena are exhibited by the room temperature superconductive materials. Furthermore, the capsule could be attached to a tether such that the capsule could be removed in the event that the natural muscular (peristaltic) movement of the digestive tract does not expel the capsule, or if the capsule is deployed in a cavity or lumen wherein the capsule must be manually removed. Furthermore, the capsule is not limited to being deployed in humans; the capsule can also be deployed in animals. Therefore, the spirit and scope of the invention should not be limited to any particular combination of elements in the versions described above.
Applicant claims the benefit of and priority to U.S. Provisional Patent Application No. 61/262,100, filed Nov. 17, 2009.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2010/002996 | 11/17/2010 | WO | 00 | 6/8/2012 |
Number | Date | Country | |
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61262100 | Nov 2009 | US |