Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-02-01
2001-05-08
Walberg, Teresa (Department: 3742)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S424000, C128S899000
Reexamination Certificate
active
06230038
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the treatment of organs, tumors, and other internal structures of living bodies with therapeutic radiation, and to methods and systems adapted to the location and therapeutic treatment of such internal structures by the use of implanted magnetic elements and magnetic fields.
BACKGROUND OF THE INVENTION
There are numerous examples where specific hidden positions within items, animals or humans need to be determined with accuracy. For example, It is generally acknowledged by oncologists that directing a source of radiation accurately at an internal tumor (e.g. carcinoma) for treatment is difficult because the precise location of the tumor is elusive. As a result, substantial amounts of radiation frequently miss the intended target, i.e. the tumor or unwanted cellular growth. This leads to the danger of radiating healthy body tissue, giving rise to tissue damage and extensive bleeding, at times from vital organs in the vicinity of the tumor.
Under the best of circumstances, preparation for radiation treatment includes obtaining tomographic images of the tumor and surrounding tissue, typically recorded several days prior to the onset of radiation treatment. The 3-D reconstruction of the images results in accurately locating the tumor in relation to the body as a whole. However, since radiation treatment may occur over a matter of months, there can be considerable shifts or displacements of the organ-containing tumor from the position originally determined from the tomograph. As a result, relying on the original tomographic positioning data can result in the radiation beam missing the target (tumor or other internal structure) either partially or even completely, striking instead regions not meant to be irradiated.
OBJECTS OF THE INVENTION
Several novel methods are presented for determining the position of remotely located regions not visible to the eye. The main emphasis of the invention is to improve the ability to accurately direct radiation onto tumors or unwanted cell growths by certain magnetic markers.
Since these positions are visually imperceptible it is proposed here to embed some type of locator such as a transmitter or the like that can emit an energy field which is detectable externally. From the amplitude and angular dependence of the detected signal as a function of position, it is then possible to deduce the precise location of the magnetic element. Such position determinations are especially important in the field of oncology where precise location of a tumor or other internal structure of a living body needs to be known prior to administering radiation treatment.
This application proposes the use of specially shaped high permeability, preferably non-linear magnetic materials that can serve as remotely positioned locators. Typically these materials are embedded in a living body and out of visual contact. Exposure to a low frequency ac magnetic field causes the radiation of non-linear magnetic fields to emanate from the magnetic material which can be detected by one or more externally located pickup coils or other magnetic sensors. A frequency analyzer may be used to examine one or more higher harmonics emitted by non-linear magnetic material Fields from ferrous solids can also be mapped in an externally applied dc field as can permanently magnetized objects without the application of an externally applied field. If the material has a sharp Barkhausen jump as is the case for certain amorphous magnetic wires (produced for example by the Unitika Corporation, of Hyogo, Japan), flux re-entrant reversals occur in the presence of a small applied ac field. These sudden magnetic reversals give rise to voltage spikes when sensed by a pickup coil. Filtering of the ac field in the sensing circuit makes it possible to map these pulses as a function of position enabling the determination of the wire's location.
While the present invention has other applications, the preferred embodiments relate to medical applications, specifically, locating tumors for radiation treatment. Small amounts of magnetic material in the form of spheres or short lengths of amorphous wire are first implanted in or near the tumor. Once location of the implant is determined by way of the magnetic field mapping, that is magnetic amplitude as a function of position, the radiation beam can be directed precisely to the target area.
SUMMARY OF THE INVENTION
The present invention broadly provides a method of determining the location of an internal structure of a living body comprising the steps of:
a) implanting, at the aforesaid internal structure, an element comprising a magnetic material to identify a selected location of the internal structure, the element being capable of emitting a magnetic signal in response to an applied magnetic field,
b) irradiating the element with an applied magnetic field,
c) detecting the magnetic signal from a plurality of selected mutually displaced positions to produce a corresponding plurality of element-locating signals, and
d) converting the element-locating signals to a location image of the internal structure.
For the purpose of therapeutic treatment of a tumor or other internal structure, the method includes a further step of e) focussing a selected degree and duration of therapeutic radiation at a target determined from the aforesaid location image of the aforesaid element.
The present invention further provides a system for determining the location of a tumor or other internal structure of a living body after implantation, at the aforesaid internal structure, of an element comprising a magnetic material to identify a selected location of the internal structure, the element being capable of emitting a magnetic signal in response to an applied magnetic field. The inventive system comprises: a) a magnetic field generator for irradiating the aforesaid element with an applied magnetic field, b) a movable magnetic field sensor for detecting the aforesaid magnetic signal from a plurality of selected mutually displaced positions to produce a corresponding plurality of element-locating signals, and c) a computing apparatus for converting these signals to a location image of aforesaid tumor or other internal structure.
For the the purpose of therapeutic treatment of a tumor or other internal structure, the system further comprises d) a controlled source of therapeutic radiation for focussing a selected degree and duration of therapeutic radiation at a target determined from the aforesaid location image of the aforesaid element.
According to a preferred embodiment of the invention, the applied magnetic field is spatially and temporally uniform, sometimes called a “dc” field.
Alternatively, applied magnetic field may be a low frequency ac (e.g. 60 Hz) magnetic field and the magnetic signal is non-linear in response to this low frequency ac magnetic field.
According to a preferred embodiment, the applied magnetic field is an ac field and the element comprises an amorphous magnetic material, said magnetic signal being characterized by non-linear Barkhausen jumps in response to this applied ac magnetic field.
Preferably, the embedded element is coated with absorbing material which absorbs therapeutic radiation (e.g. lead) and is pervious to magnetic fields. The element may last be coated with a biologically inert material (e.g. PMMA, or polymethyl methacrylate) to prevent injury to the living body in which the element is to be embedded.
According to another preferred embodiment of the invention, the aforesaid embedded element may comprise a permanently magnetized material. For this embodiment, the method of determining the location of an internal structure (e.g. tumor) of a living body comprises the steps of:
a) implanting, at the aforesaid internal structure, an element comprising a permanently magnetized material to identify a selected location of the aforesaid internal structure, this element being capable of emitting a magnetic signal,
b) detecting the aforesaid magnetic signal from a plurality of selected mutually disp
von Gutfeld Robert Jacob
Ziegler James Francis
August Casey P.
Dahbour Fadi H.
International Business Machines - Corporation
Walberg Teresa
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