Image analysis – Applications – Biomedical applications
Reexamination Certificate
1997-09-30
2003-02-04
Mehta, Bhavesh (Department: 2621)
Image analysis
Applications
Biomedical applications
C382S132000, C250S492100, C250S584000
Reexamination Certificate
active
06516081
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of and system for processing a radiation image and more particularly to a method of and system for processing a radiation image which is taken using an irradiation field stop.
2. Description of the Related Art
It has been put into practice to photoelectrically read out a radiation image recorded on a radiograph film thereby obtaining an image signal representing the radiation image, carry out an adequate image processing on the image signal and output the processed image signal to a CRT, a laser printer or the like. Further there has been known a radiation image recording and reproducing system in which a medical radiation image such as of a human body is stored on a stimulable phosphor sheet, the stimulable phosphor sheet is then exposed to stimulating rays such as a laser beam which cause the stimulable phosphor sheet to emit light in proportion to the stored radiation energy, the light emitted from the stimulable phosphor sheet is photoelectrically detected and converted to an electric image signal, and the radiation image of the object is reproduced as a visible image on the basis of the electric image signal.
In such a radiation image recording and reproducing system, the recording system, read-out system, image processing system, CRT, laser printer and the like are not always installed in one location in a hospital but are often in separate locations and connected with each other by a network. Further, an image signal representing a radiation image recorded in a big hospital is sometimes transferred to a remote hospital without a large equipment such as a recording system through a network and a visible image is reproduced on a CRT in the hospital for diagnosis.
In order to minimize the irradiation dose to the object, a radiation image is sometimes recorded using an irradiation field stop so that only a necessary portion of the object is exposed to the radiation. The image signal representing a radiation image taken using an irradiation field stop is sometimes subjected to an image processing so that the image in the irradiation field becomes more suitable for diagnosis. See, for instance, Japanese Unexamined Patent Publication No. 3(1991)-98174. For example, when a radiation image taken using an irradiation field stop is reproduced on a CRT as it is, the area outside the irradiation field is reproduced at a high brightness on the CRT, which makes it hard to see the image. Accordingly the image signal is sometimes subjected to an image processing for lowering the brightness of the area outside the irradiation field. This processing is equivalent to a processing for increasing the density of the area outside the irradiation field in film output. (Such processings will be referred to as “off-field darkening processing”, hereinbelow.)
When transferring an image signal to a CRT or the like through a network, necessary image processings are generally carried out on the image signal before transfer in order to lighten the load on the system to which the image signal is to be transferred and the network, so that only the smallest necessary image signal, that is, the processed image signal is transmitted. It is true also for the image processing for making the area in the irradiation field to easy to see. That is, an irradiation field recognition processing is first carried out on an original image signal, thereby obtaining irradiation field information for distinguishing the area inside the irradiation field from the area outside the same (information representing the irradiation field or information representing the edge of the irradiation field, i.e., the boundary between the area inside the irradiation field and the area outside the irradiation field), for instance, an off-field darkening processing is carried out on the original image signal on the basis of the irradiation field information, and then the processed image signal is transferred to the output system such as a CRT, a laser printer or the like through a network.
Generally in the image processing system using a network, when the receiver side cannot obtain a normal image signal due to abnormality on the transmitter side, the transmitter side tries again the step where the abnormality occurred and transmits again the normal image signal.
However in the case where abnormality occurs in a processing for recognizing an irradiation field (e.g., an automatic prospective irradiation field recognition processing) and a part of the image is made invisible due to the abnormality, e.g., darkened though the image signal itself is normal, it is sometimes preferred that the image be made visible at once by cancelling the processing, even if the image becomes somewhat difficult to view, rather than repeating the processing taking a long time.
Further, there is a case where it is preferred that the irradiation field be corrected on the receiver side and the image processing be carried out on the basis of the corrected irradiation field.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a method of and a system for processing a radiation image in which an image output on the receiver side with an area considered to be outside a prospective irradiation field can be processed in a predetermined way and changed with the prospective irradiation field or cancelled with the processing in a short time.
In accordance with the present invention, an irradiation field recognition processing for recognizing a prospective irradiation field which is considered to be an irradiation field of a radiation image is carried out in an image information obtaining section, which is an image signal transmitter, and the information on the prospective irradiation field is transferred to an image output section, which is an image signal receiver, attached to a radiation image signal representing the radiation image or separately therefrom, and the image processing is carried out on the basis of the transferred information on the prospective irradiation field in the image output section.
That is, in accordance with a first aspect of the present invention, there is provided a method of processing a radiation image comprising the steps of
obtaining an image signal representing a radiation image and a prospective irradiation field information representing a prospective irradiation field of the radiation image,
transferring the prospective irradiation field information attached to the radiation image signal or separately therefrom to an image output section,
carrying out an image processing to make the image in the prospective irradiation field more suitable for viewing on the transferred image signal in the image output section on the basis of the prospective irradiation field information transferred, and
outputting a radiation image on the basis of the processed image signal.
The prospective irradiation field information may be obtained by various methods. For example, the prospective irradiation field information may be obtained by carrying out an automatic recognition processing on the image signal according to a predetermined algorithm as disclosed in U.S. Pat. Nos. 4,967,079 and 5,068,907 and and the like, or may be obtained by the operator designating a prospective irradiation field using an input means such as a mouse, a touch pen or the like viewing a radiation image displayed on a monitor.
As a method of automatically detecting a prospective irradiation field by carrying out a processing according to a predetermined algorithm, various known irradiation field recognition processings may be applied. For example, a dynamic contour extraction processing using Snakes algorithm may be employed as well as a processing in which prospective edge points are detected on the basis of differences between image signal components and a prospective edge is detected on the basis of the prospective edge points.
The term “prospective irradiation field” means an area which is considered to be an i
Shimura Kazuo
Takeo Hideya
Chawan Sheela
Mehta Bhavesh
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