Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-09-28
2004-10-12
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C378S065000
Reexamination Certificate
active
06804548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an irradiation system used for radiation therapy administering radiation to an irradiation target such as a tumor, and more particularly to an irradiation system and its irradiation target movement monitoring method, and an irradiation target position recognizing method that can administer radiation by precisely recognizing position and direction of an irradiation target without using a positioning frame, while directly monitoring the position and direction of the target being irradiated.
2. Description of Related Art
The radiation therapy is a treatment to reduce or eliminate tumors by intensively administering radiation to the tumors of a patient. To achieve such a radiation therapy, it is necessary to administer radiation to a tumor, a target to be irradiated, intensively and in proper amount. At the same time, it is necessary to decrease radiation exposure to surrounding healthy tissue as much as possible.
Thus, the radiation therapy is carried out such that excessive irradiation to the tumor and its surrounding healthy tissue is suppressed by administering radiation from multiple directions with particular emphasis on the tumor as the irradiation target, so that only the tumor is intensively irradiated.
To achieve effective radiation only to the target intensively and precisely, it is essential to measure the position and direction of the target, and to decide the pros and cons of the irradiation by computing the relative position and direction between the target and a irradiation head from the computed results.
More specifically, a set of image data of an irradiation region including the target tumor is captured before irradiation, and the relative position and direction between the target and the irradiation head is measured from the set of image data, thereby planning the radiation therapy treatment in terms of the directions and irradiation dose along with the duration and the number of times of the irradiation to implement the radiation therapy according to the plan.
In such a radiation therapy as described above, there is a method to bury a marker near the target tumor, as one of the techniques to measure the position and direction of the target accurately. In this method, fixing the relative position and direction between the marker and irradiation head will enable the position and direction between the target and irradiation head to be measured with respect to the marker regardless of the variations in the position and direction of the target due to movement of the patient, and hence allows the radiation with fixing the relative position and direction between the target and irradiation head.
This method, however, is greatly invasive to the patient in that the marker is buried into the body. Thus, it is preferable to avoid this method as much as possible considering the stress imposed on the patient.
In view of this, another radiotherapy is proposed that can accurately measure the position and direction of the target non-invasively without setting the marker in the body of the patient. This method fixes a solid frame made of metal or the like on the surface of the head of the patient to precisely measure the position and direction between the target and irradiation head with respect to the frame, and administers radiation with fixing the relative position and direction between the target and the irradiation head.
This method utilizes the fact that there is little movement due to respiration or the like within the head because the brain is placed in the skull. Fixing the frame on the surface of the head and maintaining the fixed position can almost fix the relative position and direction between the frame and the target throughout the radiation. Furthermore, the relative position and direction between the frame and the irradiation device (irradiation head) can be accurately measured by fixing the frame on a treatment table or by installing a position and direction sensor on the frame.
Thus, the precise measurement of the position and direction of the frame enables precise position recognition and irradiation of the target tumor.
However, since the frame is usually fixed on the patient from the time of image measurement of the irradiation region including the target tumor for planning the radiation therapy to the time of administering the actual irradiation, the stress imposed on the patient is considerable. In addition, since the frame is fixed rather strong to prevent the frame from shifting, it is unavoidable that the patient has feelings of restraint and pressure. Thus, position recognition of the target tumor without using the frame, if implemented, will serve to improve the therapeutic environment of the patient.
As techniques of implementing the non-invasive radiation therapy of a head region, there are “Repeat fixation for frameless stereotactic procedure” disclosed in U.S. Pat. No. 5,588,430, and a radiocamera system of Kobayashi Sofamor Danek utilizing this patent.
FIG. 5
schematically shows a configuration for recognizing the position of an irradiation target in the conventional irradiation system, the “Repeat fixation for frameless stereotactic procedure” disclosed in the foregoing U.S. Pat. No. 5,588,430. In this figure, the reference numeral
51
designates a patient's head including an irradiation target tumor;
52
designates a treatment table on which the patient lies down; and
53
designates a head ring with a structure simpler than the conventional frame, for securing the patient's head
51
to the treatment table
52
. The reference numeral
54
designates a bite plate having LEDs (Light Emitting Diodes) mounted thereon for measuring the position of the body surface of the patient; and
55
designates a mouthpiece that has the bite plate
54
attached thereto, and is bitten by the patient.
Next, the operation of the conventional method will be described.
First, the patient's head
51
is secured to the treatment table
52
by the head ring
53
. Then, the bite plate
54
serving as a marker for measuring the position and direction is attached to the mouthpiece
55
the patient bites. The bite plate
54
is almost immobilized with respect to the patient's head
51
during the radiation. Accordingly, the relative position and direction between the bite plate
54
and the irradiation target in the head
51
is assumed to be almost invariable. Therefore, measuring the three-dimensional position and direction of the bite plate
54
makes it possible to estimate the position and direction of the target tumor indirectly.
In addition, since the irradiation system allows the patient to be precisely repositioned by only biting the bite plate
54
, it is unnecessary for the patient to wear the head ring
53
in the second and the following radiation, thereby reducing the stress on the patient during the therapy.
With the foregoing configuration, the conventional irradiation system is effective for the radiation therapy to a head region. However, it presents a problem in that the irradiation accuracy is degraded in trunk regions such as abdominal organs that are more affected by the body movement like respiration than the head region is, and that are continuously fluctuating the position and direction of the irradiation target.
This problem will be described in more detail.
In the radiation therapy applied to a tumor emerging in a trunk region such as an abdominal organ, since the effect of the body movement like respiration is greater than in the head region, the position and direction of the target tumor continues to vary during the irradiation. Thus, the variations in the position and direction of the irradiation target due to changes in the patient's posture become greater than those expected in the planning of the radiation therapy. In addition, being different from the head region, the trunk region usually has no bones usable for fixing a frame near the target tumor, which makes it difficult for the frame to be secured on the bod
Muroi Katsunobu
Nakajima Yoshikazu
Takahashi Shuichi
Mitsubishi Denki & Kabushiki Kaisha
Smith Ruth S.
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