Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Light application
Reexamination Certificate
1999-07-19
2001-05-29
Mulcahy, John (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Light application
C607S091000, C607S092000, C359S201100, C606S010000, C606S011000, C606S012000
Reexamination Certificate
active
06238426
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the use of an ultrasonic transducer to monitor the status of an internal diseased tissue, and more specifically, to monitoring the condition of an internal treatment site during the course of medical treatment administered to the site.
BACKGROUND OF THE INVENTION
Photodynamic therapy (PDT) has been shown to be very effective in destroying diseased tissue and tumors using light that is absorbed by a photoreactive agent previously administered to a patient. The photoreactive agent is selectively preferentially absorbed by or linked to abnormal or diseased tissue and has a characteristic absorption waveband to which the waveband of the light administered to the patient corresponds. When activated by the light, the photoreactive agent produces compounds, such as singlet oxygen, that destroy the abnormal tissue.
While much of the earlier work in PDT has been directed to treating surface lesions, perhaps a much more important application is in destroying internal tumors within the body of a patient. PDT may be administered interstitially using light from an external laser that is coupled to a plurality of optical fibers. The optical fibers convey the light into a tumor mass within a patient's body; however, interstitial PDT has been used preclinically and clinically on only a very limited basis. The clinical application of interstitial PDT to oncology has been associated with several significant problems, including inadvertent damage to normal tissue, tumor regrowth, lack of efficacy, and surgical risk related to surgical emplacement of multiple optical fibers to assure adequate light delivery to relatively large tumor masses. The damage to normal tissue can occur during PDT and can be highly variable due to the non-homogeneous distribution of the photoreactive agent within a tumor and within normal tissue surrounding a tumor, and differences in the intensity and penetration depth of light into heterogeneous tumor tissue. Portions of a tumor may be destroyed, while other portions survive and remain viable, leading to tumor cell repopulation and regrowth of the tumor mass. Unintended destruction of normal tissue can have serious consequences, which is contrary to the intended goal of completely destroying the tumor, while sparing the normal tissue.
Monitoring tumor fluorescence has been suggested in the prior art as a possible way to determine the border of a tumor relative to normal tissue before beginning to administer PDT. However, there is no teaching in this prior art of monitoring the effect of PDT in real time to assess its progress in destroying diseased tissue nor any teaching of how to determine the effects of light distribution in a tumor. Other methods that have been proposed to monitor a tumor's condition include using radioactive-labeled agents to monitor blood flow in vessels supplying the tumor. These methods suffer from lack of repeatability, poor resolution at a boundary between a tumor and normal tissue, and inconvenient image capture. To implement such methods, it is typically necessary to transport a patient to specially fitted suites in which the imaging equipment is installed or to move relatively large imaging devices into the proximity of the patient. Also, toxicity due to repeated injection of radionuclides into a patient is a concern, since once an injected radionuclide is trapped within thrombosed and occluded vessels at the treatment site, there is no practical method to rapidly clear the trapped radionuclide material for another injection, in order to asses further vessel shut-down.
Thus, no practical method is disclosed in the prior art for real-time monitoring of interstitial PDT in order to assess the changing extent of tumor destruction and to avoid damage to surrounding normal tissue as the treatment progresses. Typically, since the photoreactive agent is administered to a patient as a bolus so that its concentration within the patient's body cannot thereafter be controllably varied other than by giving additional doses, the only available control in administering PDT is in regard to the light intensity, duration of light administered, the timing of light administered, and the total light dose administered to a treatment site. It would therefore be desirable to develop a technique for providing PDT that enables real-time monitoring of an internal treatment site, so that one or more of these parameters can be varied in response to changes in the treatment site as the PDT continues. Such a method would allow practical, cost-effective, and non-invasive determination of the effects of the PDT on a tumor at a treatment site and its progress in destroying the tumor, and would provide guidance in varying one or more of the parameters noted above to achieve a substantial clinical benefit at minimal risk to the patient.
SUMMARY OF THE INVENTION
In accord with the present invention, a method is defined for administering light therapy to diseased tissue at an internal treatment site within a patient's body for an extended period of time, wherein the light therapy is modified in response to a condition of the internal treatment site. The method includes the step of providing a light source that emits light within a predetermined waveband. A photoreactive agent having a characteristic light absorption waveband that corresponds to the predetermined waveband in which light is emitted by the light source is administered to the patient. Subsequently, light is administered to the diseased tissue with the light source, and the light therapy continues over the extended period of time. At a plurality of times, including at least one time after an onset of administering the light, the internal treatment site is ultrasonically scanned to produce a plurality of images, each image indicating a condition of the internal treatment site at that time. By comparing an image of the internal treatment site made at a time after the onset of administering the light therapy with an image made at an earlier time, changes in the condition of the internal treatment site are detected. The light therapy is then modified in response to a change in the internal treatment site that has been thus detected.
The step of ultrasonically scanning preferably includes the step of scanning the internal treatment site before the onset of administering the light therapy, to produce a baseline image of the diseased tissue at the internal treatment site before the diseased tissue has experienced any effect from the light therapy. To determine a change in the internal treatment site, the baseline image is compared with a subsequent image made a substantial time after the onset of administering the light therapy. Alternatively, the internal treatment site can be scanned before a substantial amount of light therapy has been administered, to produce a quasi-baseline image of the diseased tissue at the internal treatment site before the diseased tissue has been substantially affected by the light therapy. In this case, the change in the internal treatment site is determined by comparing the quasi-baseline image with a subsequent image made a substantial time after the onset of administering the light therapy.
In one embodiment of the present invention, the light source preferably comprises a probe in which at least one light source is disposed and which is adapted to be interstitially inserted within the diseased tissue at the internal treatment site. Alternatively, the light source comprises an optical fiber having a distal end adapted to be interstitially inserted into the diseased tissue and thus able to convey light into the treatment site from a light emitting source that is disposed outside of the patient's body. In yet another embodiment, the light source is disposed outside of the patient's body while administering the light therapy, and the predetermined waveband includes wavelengths sufficiently long to penetrate normal tissue overlying the internal treatment site to reach the diseased tissue without an optical
Anderson Ronald M.
Farah Ahmed
Light Sciences Corporation
Mulcahy John
LandOfFree
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