Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-25
2001-02-13
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S412000, C601S003000
Reexamination Certificate
active
06188923
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for local heating and global monitoring of a tissue disposed in an imaging device, monitored by the imaging device and heated substantially simultaneously by focused ultrasound. The invention also relates to an apparatus for local heating and global monitoring of a tissue, including an imaging device for receiving the tissue and monitoring the tissue, as well as a source for generating ultrasound.
The invention relates in particular to a method and an apparatus for treating and in particular destroying a selected zone within a tissue in the human body. The tissue is heated for a sufficient length of time, by focusing ultrasound, to a comparatively high temperature sufficient to kill the tissue. The focus of the ultrasound, that is the region in which the energy of the ultrasound attains sufficiently high intensity, is typically approximately 3 mm in diameter and approximately 10 mm in length. If there is a need to treat a larger zone of tissue, then the zone can be divided up into an appropriate grid and treated appropriately by variable focusing of the ultrasound. Both the monitoring of the temperature attained in the zone, and the distribution of that temperature, are of major importance. It is especially critical to prevent the destruction of healthy tissue located immediately adjacent diseased and especially tumorous tissue. Efforts are therefore made to monitor the temperature distribution in a tissue treated with focused ultrasound.
A magnetic resonance scanner with a support for a patient who is to be treated and with a source for focused ultrasound built into the patient support, is sold by the General Electric Company. In that apparatus, complicated provisions for electromagnetic shielding are necessary, in order to prevent the source from impeding the operation of the magnetic resonance scanner itself. A complicated safeguard to protect the patient to be treated against electric currents from the source is also provided.
A paper entitled “Temperature Monitoring of Focused Ultrasound Therapy by MRI”, by P. Huber, in Ultrasonics Symposium 1994, pages 1825 ff., describes a combination of a source for focused ultrasound and a magnetic resonance scanner, in which the source and the magnetic resonance scanner are operated in alternation. The magnetic resonance scanner is set up in such a way that it can detect and display both the location of the focus and the temperature distribution in the tissue being treated.
Fundamental information on temperature measurement through the use of magnetic resonance imaging using a contrast medium is found in a paper entitled “Non-Invasive In Vivo Temperature Mapping of Ultrasound Heating using Magnetic Resonance Techniques”, by N. B. Smith, in Ultrasonics Symposium 1994, pages 1829 ff.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and an apparatus for local heating and global monitoring of a tissue, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and apparatuses of this general type and in which treatment of a tissue by ultrasound with substantially simultaneous monitoring by an imaging device can be performed without interference and without the possibility of unintended damage to the tissue.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for local heating and global monitoring of a tissue, which comprises placing a tissue in an imaging device; monitoring the tissue with the imaging device; and substantially simultaneously heating the tissue with focused ultrasound generated outside the imaging device and guided to the tissue by a waveguide.
Accordingly, along the lines of the invention, the close connection between the source for the ultrasound and the imaging device that was always required previously has been done away with. All that is required for introducing the ultrasound, required for treating the tissue, into the tissue is a waveguide. Any electronic circuit for generating the ultrasound, which at least when it is intended to suit the purposes discussed at the outset must include a power amplifier for furnishing relatively high-power ultrasound, and which would thus be fundamentally quite capable of causing extensive electromagnetic interference, can be disposed away from the imaging device and shielded off in every respect. Only the waveguide is in close spatial contact with the imaging device. This waveguide must pass only acoustical and not, for instance, electromagnetic signals into the imaging device, and thus it is not itself an independent source of electromagnetic interference. In particular, the waveguide may be constructed as an electrical insulator.
In accordance with another mode of the invention, the imaging device operates with at least one electromagnetic field at an associated operating frequency, the ultrasound has an associated ultrasonic frequency, and the at least one operating frequency is different from every integral multiple of the ultrasonic frequency. It is thus assured that because of the distinction between the operating frequency and the ultrasonic frequency and its integral multiples, largely interference-free operation of the imaging device is assured. Thus the spatial distancing between the imaging device and the source is augmented with functionally dictated distancing, since the possibility of electromagnetic influence on the imaging device from the source is reduced even further.
In accordance with a further mode of the invention, a power level at which the ultrasound heats the tissue is measured. This measurement can be performed with known measuring instruments of various kinds. In particular, a thermooptical measuring instrument can be employed. In this measuring instrument, the energy of the ultrasound is converted into heat in a corresponding absorber and is measured as a temperature through the use of a fiber optic sensor. This offers an additional opportunity for monitoring the effect of the ultrasound, thus making the method substantially safer in use.
In accordance with an added mode of the invention, the ultrasound has chronologically variable focusing. Therefore, the spatial location of the area in the tissue that is particularly affected by the ultrasound can be shifted, thus making a relatively large zone in the tissue accessible to the ultrasonic heating.
In accordance with an additional mode of the invention, the imaging device operates through the use of magnetic resonance imaging. Magnetic resonance imaging is an especially gentle method for treating a tissue and is thus especially well suited for use within the context of medicine.
In accordance with yet another mode of the invention, a magnetic resonance imaging method is employed in which monitoring of the temperature distribution in the tissue is possible, making the consequences of the treatment with ultrasound immediately detectable. In particular, the monitoring of the temperature distribution can be carried out on the basis of a contrast medium introduced into the tissue beforehand.
In accordance with yet a further mode of the invention, the local heating or thermal treatment and the global monitoring of the tissue are performed jointly and simultaneously. To that end, the invention provides a favorable precondition for avoiding mutual influence between the imaging device and the source.
In accordance with yet an added mode of the invention, the tissue is heated through the use of the ultrasound locally to a temperature between 60° C. and 90° C. This allows the use of the method to destroy a diseased and in particular tumorous area in living tissue. A major contribution to this capability is the possibility that the effect of the ultrasound on the treated tissue can be monitored immediately in chronological terms. This is because the tissue can be monitored globally, that is over an area having a comparatively small part which is a zone to be treated with the ultrasound. This thus allows drawin
Greenberg Laurence A.
Lateef Marvin M.
Lerner Herbert L.
Shaw Shawna J.
Siemens Aktiengesellschaft
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