X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-08-25
2001-07-31
Porta, David P. (Department: 2876)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S020000
Reexamination Certificate
active
06269143
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a radiotherapy planning system for making a treatment plan, such as determining an irradiation field shape, in advance of treating disease such as cancer with radiation.
(2) Description of the Related Art
In treating disease such as cancer with radiation, the diseased part must be irradiated properly. For this purpose, a radiotherapy planning system is used to acquire images of and around the diseased part by means of an X-ray CT apparatus and a fluoroscopic apparatus, and to determine an irradiation field shape coinciding with an outline of an image of the diseased part appearing in an image acquired.
Such a radiotherapy planning system often includes a CT simulator and an X-ray simulator. The CT simulator has an X-ray CT apparatus as a main component thereof, while the X-ray simulator has an X-ray TV apparatus as a main component thereof. These simulators have certain additional functions, respectively. First, CT radiography is carried out using the CT simulator to acquire a plurality of sectional images. These sectional images are combined to reproduce a three-dimensional image, and then an oblique image (transmitted image seen from one direction) is produced therefrom. Alternatively, CR images which are fluoroscopic images are photographed by linearly moving a CT detector. These simulation images are displayed to identify a diseased part to be treated.
Next, an irradiating angle is determined from sectional images of a wide region including the diseased part or a transmitted image, seen from a particular direction, produced from a three-dimensional image obtained by combining the sectional images. A transmitted image seen from the irradiating angle is displayed. Then, the operator determines a shape of an irradiation field on the image displayed, and sets an isocenter to the irradiation field. Further, a position corresponding to the isocenter is marked on the patient's surface (skin surface).
Subsequently, the patient is positioned relative to the X-ray simulator by using the mark on the skin surface as a reference, so that the mark coincides with the isocenter of the X-ray simulator. An X-ray irradiating angle corresponding to the irradiating angle determined as above is set to the X-ray simulator, and an image is photographed on a film through radiography for use as a reference photograph for collation.
Further, the patient is positioned relative to a radiation treating apparatus by using the mark on the skin surface as a reference, so that the mark coincides with the isocenter of the treating apparatus. An irradiating angle is set to the irradiating angle determined as above, and film radiography is carried out by emitting radiation. This radiation film image is collated with the above X-ray film image acting as the reference photograph to confirm that the patient has been positioned according to plan.
After this is confirmed, radiotherapy is performed for the diseased part by actually emitting radiation from the radiation treating apparatus.
However, the conventional radiotherapy planning system has a drawback of not always assuring a treatment plan made for irradiating a diseased part with an appropriate irradiation field shape.
That is, in the conventional system, an oblique image or the like produced from sectional images acquired from the CT simulator is a still picture, and therefore cannot accurately reflect in the treatment plan the movement of internal organs and the like due to respiration and other functions. Further, fluoroscopic images are conventionally acquired with the X-ray simulator using an image intensifier. The fluoroscopic images acquired are distorted by curvature of the X-ray incidence surface. When an irradiation field shape is verified on a fluoroscopic image, the field shape fails to exhibit a reliable geometrical conformity to the actual diseased part.
SUMMARY OF THE INVENTION
This invention has been made having regard to the state of the art noted above, and its object is to provide an improved radiotherapy planning system for properly making an irradiation field shape for radiation treatment according to an actual shape of a diseased part.
The above object is fulfilled, according to this invention, by a radiotherapy planning system for making a treatment plan for radiation treatment, comprising:
a CT simulator including a CT image pickup gantry having an X-ray tube and an X-ray detecting device, a pointer for indicating an irradiation center, and a patient supporting device;
an X-ray simulator including an X-ray tube, a flat panel imaging system for medical X ray and a patient supporting device;
a setting device for setting an irradiation field shape and an irradiation center on an image acquired from the CT simulator; and
a superposing and displaying device for displaying a fluoroscopic image acquired from the X-ray simulator, with the irradiation field shape superposed thereon.
With this construction, a fluoroscopic image acquired from the X-ray simulator is displayed with, superposed thereon, an irradiation field shape determined beforehand. Thus, the validity of the field shape may be checked by using the fluoroscopic image. The fluoroscopic image, which is acquired from the flat panel imaging system for medical X ray, is free from distortion and has a high degree of geometrical conformity to the image acquired from the CT simulator. The fluoroscopic image is superior in image quality to the image acquired from the CT simulator, and may be displayed as a dynamic image. By using the fluoroscopic image having such features, the field shape may be checked easily and accurately. Even when the site to be treated has moved with the patient's movement, an appropriate field shape may be determined by taking such movement into account since the operator can observe the dynamic image.
The image collecting system in the X-ray simulator consists only of the light and small flat panel imaging system for medical X ray. There is no need to use a heavy and bulky combination of an image intensifier and a TV camera used in the prior art. Thus, without requiring a support structure of great strength, fluoroscopic images may be picked up from varied angles with enhanced geometrical precision such as precision in imaging angle. The X-ray simulator, though having a simplified and inexpensive construction, can provide fluoroscopic images with increased accuracy. Consequently, while achieving economy, the field shape may be checked accurately and properly by using fluoroscopy.
In the above radiotherapy planning system, the setting device and the superposing and displaying device may comprise a computer. With this construction, the setting device and the superposing and displaying device are realized in a simple way, and the system may be downsized and simplified.
Images acquired from the CT simulator and images acquired from the X-ray simulator may be processed by one computer.
With this construction, a treatment plan may be made efficiently while operating the computer to display each of the images acquired from the CT simulator and X-ray simulator.
In the above radiotherapy planning system, one patient supporting device may be shared by the CT simulator and X
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ray simulator.
This construction has a reduced number of components to achieve compactness and low cost of the system. The two simulators can pick up images of the patient supported on the one patient supporting device. The patient need not be placed on or removed from the patient supporting device while picking up images necessary to make a treatment plan. There is a reduced chance of variations in patient's position relative to the patient supporting device, which facilitates positional adjustment of the patient to each simulator.
Where one patient supporting device is shared by the two simulators, the CT simulator and X-ray simulator may be arranged around the one patient supporting device which is pivotable about a support axis. Thus, with the patient directed to the CT simulator by turning the one
Arent Fox Kintner
Plotkin & Kahn PLLC
Porta David P.
Shimadzu Corporation
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