MRI HYPERTHERMIA TREATMENT SYSTEMS, METHODS AND DEVICES, ENDORECTAL COIL

Abstract

Hyperthermia has been applied by, for example, separate ultrasound transducers, RF or microwave transmitters and heated fluids. Imaging by separate MRI imaging coils is usually used to view the anatomical region under treatment. Separate temperature probes (needles, catheters) are often used to monitor tissue temperature. Control of the temperature profile required for effective hyperthermia treatment is usually done by trial and error, involving a human operator. The present invention combines all of these capabilities into a single device, which is MRI compatible and safe. It also allows for automatic control of the RF energy to achieve a prescribed tissue hyperthermia.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a representation of a system of the present invention.

FIG. 1B is a first embodiment of the present invention.

FIG. 1C is a second embodiment of the present invention.

FIG. 2A is an alternate embodiment of the present invention.

FIG. 2B is another alternate embodiment of the invention using a 1.5 Tesla MRI Imaging System

FIG. 2C is yet another alternate embodiment of the invention using a 3.0 Tesla MRI Imaging System

FIG. 3A is a further alternate embodiment of the invention using a dual tuned endorectal coil for imaging and heating.

FIG. 3B is another alternate embodiment of the invention using a dual tuned endorectal coil for imaging and heating.

FIG. 4A is an alternate embodiment of the invention using the host MR system as an RF source for RF heating.

FIG. 4B is a further alternate embodiment of the invention using a phased array single tuned endorectal coil.

FIG. 5A is an alternate embodiment of the invention using the Host MR System to control the selection of heating coil elements.

FIG. 5B is an alternate embodiment of the invention using a Transmit/Receive interface detail for a phased array dual tuned endorectal coil.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

FIGS. 1A, 1B AND 1C uses the existing MEDRAD BPX-10, BPX-15, and BPX-30 as a Transmit/Receive Coil. The existing prostate endorectal coils, the BPX-10 [1.0 Tesla], BPX-15 [1.5 Tesla], and BPX-30 [3.0 Tesla] can be used as a receive coil for imaging, and as a transmit coil for local RF heating of the prostate gland using RF energy at the Larmour frequency of the host MRI scanner. To accomplish this, the interface would essentially duplicate the function of the current interface devices such as the MEDRAD ATD-II in the receive mode for imaging. Further, the system body coil would be used for RF transmission during imaging. Optionally, the endorectal coil could transmit for imaging, although the transmit B1 RF field might be too non-uniform to make this a desirable practice.

The endorectal coil would operate as a transmit coil to achieve RF heating of the prostate gland. The RF power could be obtained from the Head Coil Port on earlier GEHC MR systems, or from the Surface Coil Port that contains a transmit port on later GEHC systems, all Siemens MR systems, and new Philips MR systems. The new interface device could use the endorectal coil as a transmit coil; at 3.0 Tesla, the endorectal coil is ready to operate in this mode if driven by balanced RF energy source having a characteristic output impedance to the endorectal coil of 200 ohms balanced [in the format of two 50 ohm unbalanced lines with a 180° difference in the phase of the RF drive power]. The endorectal coil is not capable of very high power operation as it is currently designed and built; however, the power handling capability is probably sufficient for the 4°-5° heating capability that is believed to be appropriate. At 1.5 or 1.0 Tesla, the endorectal coil impedance is considerably higher, on the order of 700-1000 ohms, and unbalanced. A simple matching network in the specialized interface can accomplish this. Whether the 1.0 or 1.5 Tesla endorectal coil can accept sufficient power to achieve the desired amount of heating is not yet known, since these coils are an unbalanced feed, use only one capacitor on the endorectal coil loop to series-resonate the loop, and represent a considerably higher impedance load. Potentially, 42 or 64 MHz energy may be less efficient at heating tissue than the 123-128 MHz RF energy employed at 3.0 Tesla. The fact that the 1.0 and 1.5 Tesla endorectal coils are Faraday shielded will not help the heating efficiency, either, since the Faraday shield greatly reduces the local electric field from the endorectal coil at 1.5 or 1.0 Tesla. A unique Coil Name and coil configuration file [or equivalent in non-GEHC systems] would allow the heating to be administered using the transmit/receive head coil RF power level to provide the heating energy; this can readily be done on GEHC and Siemens Medical Solutions systems, and should be possible on newer Philips systems that include at least one transmit RF port in the Surface Coil Port. Manipulation of the MRI system parameters [TR, scan type, flip angle, echo train length] can control the amount of RF heating that is generated,

FIGS. 2A, 2B and 2C show Imaging and RF Heating with Existing endorectal coil Products and a Separate RF Source. The current endorectal coil products [MEDRAD BPX-30, BPX-15, and BPX-10] could also be used with a unique interface device that was both the receive-mode interface to the host MRI scanners from GEHC, Siemens, or Philips, and also an RF energy source at an appropriate frequency for the endorectal coil in use. In this format, the RF energy source would be operating at a frequency that was at least near the Larmour frequency of the host MRI system. This would allow the new interface device to control the RF heating energy in a very exact manner, independent of the MRI scanner in use. The RF energy source could be used in the MR scanner bore, or in the MR scanner shielded room while not inside of the MR system magnet bore. The specialized interface device could possibly operate outside of the MR shielded room or scanner environment, but issues with FCC Part 15 RF radiation levels might prohibit such operation; interference issues with other local MRI systems might also be an issue if operation outside of the MR scanner shielded room is contemplated. The interface system described here would connect the endorectal coil to the host MRI scanner for imaging in the usual way; for RF heating, the interface would provide a controlled amount of RF power [probably Continuous Wave, with variable power levels] to the endorectal coil for an appropriate and controlled period of time. The endorectal coil could again be used for imaging whenever desired [as long as the endorectal coil was not being actively used for RF transmission and heating at the exact time that imaging was desired].

FIGS. 3A and 3B depict a New, Dual-Tuned endorectal coil for Imaging and RF Heating. With this configuration, the endorectal coil itself would be modified to continue to provide imaging performance as it currently does; the new endorectal coil could plug into the current interface devices sold by MEDRAD for imaging, and into a unique source of RF power for heating, or a combined interface system could be provided. The endorectal coil and RF source could operate at a frequency that is widely separated from the imaging frequency; for example, the heating RF source and the endorectal coil could operate at approximately 2450 MHz, a frequency that is the dipolar moment resonance frequency of water, and the frequency used by typical microwave ovens for the heating function, and at the MR system Larmour frequency for imaging.

The endorectal coils can be dual-tuned devices, or they could contain two separate coil systems, one for imaging, and one system for RF heating. The heating coil system could contain more than one coil element; this would allow some localization of the application of the heating. A dedicated RF source would be used with this system; the RF source could direct the RF energy to the appropriate transmit coil elements, and also control the RF power level and duration of application. There are a large number of possible variations in the hardware that would fall under this general category; the number of coil elements, the operating frequencies, and the nature of the RF power source all can rationally exist in a variety of forms.

FIGS. 4A and 4B depict an Array Coil for Imaging and Localized RF Heating at the MR System Larmour Frequency. A new endorectal coil could be developed for use with a new interface for interfacing an array coil to the host MR system and for connecting RF power from the host MRI scanner to the desired coil elements to direct the RF heating to the desired areas. The purpose of this version of the new endorectal coil system is to localize the RF heating to some degree while maintaining all operation from the host MRI scanner system. The endorectal coil could contain from two to perhaps sixteen different elements; a coil with four to eight elements is probably a practical limit. This concept would not use a separate RF source; it would employ the host MRI scanner as the RF power source, and would apply the RF heating energy at the Larmour frequency of the MRI scanner.

The control of the endorectal coil transmit elements used could be accomplished, at least on GEHC systems and probably on Siemens and Philips systems, by using unique Coil Names with different Coil Configuration File parameters to control which elements are activated; the MR pulse sequence and duration selected could set the total amount of RF heating power delivered. The receive mode could simply use all of the endorectal coil elements, a selection of the endorectal coil elements, or a specific endorectal coil element under control of the Coil Name and the Configuration File selections in the standard phased array receive manner. An endorectal coil with this level of complexity may cease to be a disposable due to cost consideration; it could be designed as a long-life device, or a device with a limited but multiple-use life.

FIGS. 5A and 5B show a Dual-Tuned Phased Array Coil for Imaging and Localized RF Heating to Use a Frequency Different from the System Larmour Frequency. A new Phased Array Dual Tuned endorectal coil could be developed for imaging and RF heating: it would require a new interface with an RF power source at a frequency other than the system Larmour frequency. The coil element selection for the RF heating could be controlled by a selection of Coil Names on the host MRI scanner to direct the RF heating to the desired areas, or it could be controlled by other local or remote means. The purpose of this version of the new endorectal coil system is to localize the RF heating from an independent source of RF power, and to maintain imaging capability from the host MRI scanner system. The endorectal coil could contain from two to perhaps sixteen different elements; a coil with four to eight elements is probably a practical limit. This concept would use a separate RF source; it could optionally employ the host MRI scanner as the control device by selecting specific Coil Names to cause the independent RF power source to apply the RF energy selectively to the various transmit array elements in the endorectal coil. The RF heating energy would operate at some frequency that is different, perhaps substantially different, from the Larmour frequency of the MRI scanner.

The control of the endorectal coil transmit elements used could be accomplished, at least on GEHC systems and probably on Siemens and Philips systems, by using unique Coil Names with different Coil Configuration File parameters to control which elements are activated. The receive mode could simply use all of the endorectal coil elements in a standard phased array receive manner. For the Transmit RF Heating mode, a selection of the endorectal coil elements, or a specific endorectal coil element would be under control of the Coil Name and the Configuration File selections. Optionally, the interface device could contain its own local control for the selection of the coil elements to be used for heat application, or a remote control or wired or wireless design could be provided. An endorectal coil with this level of complexity may cease to be a disposable due to cost consideration; it could be designed as a long-life device, or a device with a limited but multiple-use life.

It is possible to employ the same basic concepts outlined in the five invention embodiments described above to Surface coil systems other than the intracavity or endorectal coils discussed above; this can be done in combination with endorectal coils or with external surface coil devices. In each case where the endorectal coil is described in a new application and/or new configuration, the endorectal coil device could be replaced with a specific surface coil system as might be appropriate for the anatomy of interest. Because the majority of current surface coil systems are not intended to be disposable devices, and are not used with an external interface device as is done with the MEDRAD family of endorectal coils, in most instances modifications will be needed to employ existing surface coils in a manner as described above. The applications and benefits outlined in this document can in many cases be implemented to benefit with current or newly developed surface coil systems. These surface coil systems could include an endorectal coil as a part of the system, or not include one as would be appropriate for the specific application and hardware.

The surface coil system, or specific elements of it, could operate as a transmit coil to achieve RF heating of the specific target anatomy. The RF power could be obtained from the Head Coil Port on earlier GEHC systems, or from the Surface Coil Port that contains a transmit port on later GEHC, all Siemens, and new Philips systems. A new interface device could use the modified surface coil system as a transmit coil. Current receive-only surface coils are, in general, not capable of very high power operation with minimal modifications; however, the power handling capability with simple modifications may be sufficient for the 3°-10° C. heating capability that is believed to be appropriate. Again, 42 or 64 MHz energy may be less efficient at heating tissue than the 123-128 MHz RF energy employed at 3.0 Tesla. A unique Coil Name and coil configuration file [or equivalent in non-GEHC systems] plus a modified surface coil and a specialized coil interface device would allow the heating to be administered using the transmit/receive head coil RF power level to provide the heating energy; this can readily be done on GEHC and Siemens Medical Solutions systems, and should be possible on newer Philips systems that include at least one transmit RF port in the Surface Coil Port. Manipulation of the MRI system parameters [TR, scan type, flip angle, echo train length] can control the amount of RF heating that is generated. A reference concerning operating a coil device or system as a receive-only coil or, selectively, as a transmit or transmit/receive coil is given in U.S. Pat. No. 6,512,374B1, the contents of which are incorporated herein by reference.

The present invention includes several novel and unique features. It employs RF energy from a locally applied antenna [the MR endorectal coil] to the prostate gland or colon. This disclosure includes several unique features that can, in general, be used independently or in combination with other features. In one embodiment, the invention includes a MEDRAD disposable endorectal MR coil antenna, the BPX-10, BPX-15, or BPX-30, and allows the endorectal coil to be used for MR imaging of the prostate; it also makes provision for the disposable endorectal coil to be used to apply RF energy to the prostate gland to cause RF heating of the area. The RF power source can be the host MRI scanner in an embodiment of this invention, or the Interface Device included as a part of this invention may contain its own RF power source. The energy to operate the RF power source if used can come from an external source, an internal battery, or from the host MR scanner via power harvested by any one of a number of different means. These means may include DC connections to the DC power sources of the host MR system supplied at the Surface Coil Port, or from bias currents provided by the host MRI system at the port, or from a harvesting of RF energy from the host MRI system. The endorectal coil may be designed to resonate at two different frequencies, one at the Larmour frequency of the host MRI scanner, and at a second frequency removed from the Larmour frequency. The second frequency might be about 2450 MHz, the dipolar frequency of water molecules, or some other desired frequency that is not the Larmour frequency of the MR scanner. The endorectal coil may be designed to be an array coil, in the transmit, receive, or both modes. The use of array technology could allow some focusing of the applied RF power to specific regions of the prostate gland or colon. The phased array aspect of the design can be used with a single-tuned coil system operating at the host MR system Larmour frequency, or it may be dual-tuned to allow the use of a frequency other than the system Larmour frequency, such as [but not limited to] 2450 MHz.

Claims

1. A method comprising: creating an image of tissue with an MR coil;creating a temperature contour map of the tissue; andheating the tissue with the MR coil.

2. The method of claim 1 wherein the tissue is heated to a desired thermal profile.

3. The method of claim 1 wherein the MR coil is used to create the temperature contour map of the tissue.

4. A method comprising: creating an image of tissue with an MR scanner; andheating the tissue with the MR scanner.

5. A method comprising: placing an MR coil in proximity to internal tissue of a patient;creating an MR image of the internal tissue with the MR coil;heating the internal tissue with the MR coil.

6. The method of claim 5 wherein the MR coil is an endorectal coil.

7. A system comprising: an array of RF elements that can modify the deposition of energy in tissue by controlling the phase or frequency of the energy.

8. A system comprising: an antenna array; anda closed loop control system in communication with the antenna array, the closed loop control system operable to control the antenna array to match the thermal treatment plan for a patient to a measured temperature distribution in a target tissue.