X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Patent
1980-01-02
1982-09-28
Smith, Alfred E.
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
2502521, A61B 600
Patent
active
043520200
ABSTRACT:
In the X-ray CT system, the X-ray detectors vary in output characteristics such as linearity, directivity and radiation quality from one detector to another. To make compensations for such irregularities, a plurality of phantoms of different absorption is prepared in the CT system according to the present invention. Namely, this plurality of phantoms is set one by one in the measuring space in the same manner as in the examination of an examinee or subject to be examined; the coefficient of X-ray absorption is determined for each of these phantoms. Further, theoretical values of absorption for each phantom are compared to the actual absorption measurements on each phantom to provide an absorption error value for each detector at differing absorption levels. The actual subject absorption value for each detector is used to pick the two error values closest to the actual value. The two error values are interpolated or extrapolated to find an error value for correcting the actual absorption value. The above method steps are advantageously implemented by one or more digital computers. The corrected subject absorption values are provided to a conventional image reconstruction device to provide the desired X-ray video image.
REFERENCES:
patent: 3881110 (1975-04-01), Hounsfield et al.
patent: 4028554 (1977-06-01), Hounsfield
patent: 4149247 (1979-04-01), Pavkovich et al.
patent: 4225789 (1980-09-01), Albrecht
patent: 4233507 (1980-11-01), Volz
Horiba Isao
Koike Kouichi
Kuwabara Yasuo
Yanaka Shigenobu
Baker Joseph J.
Ferguson Jr. Gerald J.
Grigsby T. N.
Hitachi Medical Corporation
Smith Alfred E.
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