X-ray or gamma ray systems or devices – Electronic circuit – With display or signaling
Reexamination Certificate
1999-12-30
2001-08-21
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Electronic circuit
With display or signaling
C378S062000
Reexamination Certificate
active
06278765
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for producing diagnostic quality x-ray images from a fluoroscopic sequence. more particularly, the invention relates to a system by which the images of a fluoroscopic sequence are combined to form an image having superior quality when compared to the individual images from the sequence.
Trraditionally, x-ray imaging has been divided into two major classifications: radiography and fluoroscopy.
Radiography generally involves the transmission of x-rays through a subject, wherein x-ray photons that are not absorbed by the subject reach a receptor and form a “shadow” of the subject. The resulting static image is typically acquired in less than one second on the receptor, which may be a film-screen combination, or a solid state detector. If properly acquired, a relatively sharp, high resolution image results which is approved for a variety of diagnostic purposes.
Fluoroscopy also involves the transmission of x-rays through a subject. However, x-ray photons that are not absorbed by the subject strike a fluorescent screen, wherein a continuous image is recorded therefrom with a television camera or digital camera. The resulting real-time sequence of images can display movement. The images are typically acquired and displayed at up to thirty frames per second. Typically the image quality of a fluoroscopic image, or a sequence of fluoroscopic images, is limited by the relatively smaller number of photons reaching the receptor during the relatively short exposure time therefor.
Mammograms are conventionally not performed using fluoroscopy since fluoroscopic images inherently lack the quality necessary for critical examination. Thus, radiography is used which requires a long exposure time. To prevent motion artifacts from motion during the exposure, the breast is compressed, resulting in severe discomfort to the woman. In addition, because of the length of exposure, effective mammography in mobile screening centers is greatly reduced—making mammograms less accessible to the poor, and woman in rural or remote locations.
Generally, radiographic quality is compromised by a number of “artifacts”. Artifacts are undesirable features of an image which make using the image for diagnostic purposes more difficult. Among these are motion artifacts and quantum mottle. Motion artifacts result from movement of the patient, especially during pediatric radiography, and in theory can even result from vibration of the image acquisition equipment. Quantum mottle occurs when insufficient photons reach the receptor, and quantization occurs to flatten the image or create a mere shadow of the subject—devoid of detail. Quantum mottle is especially pervasive with fluorography, where short exposure times can rob images of crucial detail.
Other factors which influence the usefulness of an x-ray image for a particular diagnostic purpose include the interaction between different types of human tissue with the x-ray photons. In particular, x-ray photons generated with a different “kV setting” will penetrate different tissue in varying degrees. Accordingly, different kV settings will reveal different features and abnormalities in different types of tissue. However, because conventional x-rays are acquired using a single kV setting, each image is in effect a compromise of which anatomical features to emphasize.
With regard once again to fluoroscopy, several attempts have been made to increase the usefulness of fluoroscopic images. However, by there nature, these techniques are not suited for the creation of images of diagnostic quality.
One such technique, known as “image hold” attempts to improve the quality of final fluoroscopic image through the averaging of several individual frames. However, because there is no correction for motion, increasing the number of individual frames will blur an image having motion artifact.
While these units may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present invention as disclosed hereafter.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a technique for producing a diagnostic quality image from a fluoroscopic sequence. Accordingly, the individual frames from the fluoroscopic sequence are combined to create an image which has superior quality to any of the individual frames.
It is another object of the invention to provide a technique which reduces the effects of quantum mottle. Accordingly, the use of numerous frames from the fluoroscopic sequence produces the unexpected result that the subtle variations in the individual image which represent features of the subject which would be otherwise invisible to the naked eye, suddenly become visible in the resultant image.
It is another object of the invention to provide a technique which removes the distraction of motion artifacts. Accordingly, image stabilization is applied to provide a consistent reference for the resultant image, while extraneous motion becomes invisible by the very nature of the usage of multiple image frames.
It is a further object of the invention to reduce the overall radiation dosage to the patient. Accordingly, the acquisition of a multi-purpose image having superior spatial and contrast resolution, from a single fluoroscopic sequence, drastically decreases the overall exposure of the patient.
It is a still further object of the invention to provide a technique which is particularly well suited for mammography. In particular, the elimination of motion artifact by the instant invention means that the mammographic image can be acquired with less painful compression of the breast, and can be more feasibly acquired at mobile screening units. In addition, the instant invention can produce a useful image with less radiation exposure, and will produce a more useable image by virtue of the decreased compression.
It is yet a further object of the invention to provide a technique which is particularly well suited for evaluating trauma patients, the elderly, children, or any patient who has difficulty remaining still during the extended exposure necessary for a radiographic examination. Accordingly, the motion artifact eliminating properties of the present invention allow the acquisition of a useable image even in the case of such patients, and reduces the necessity for increased radiation exposure from image acquisition repetition often necessitated by moving patients.
REFERENCES:
patent: 5651042 (1997-07-01), Dewaele
patent: 5832055 (1998-11-01), Dewaele
patent: 6183139 (2001-02-01), Solomon et al.
patent: 6208709 (2001-03-01), MeLen
Goldstein Law Offices P.C.
Kiknadze Irakli
Kim Robert H.
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