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| Sequence controller |
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| Self-adjusting RF repeater arrangements for wireless telephone systems |
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| Electronic circuit for a timepiece |
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| Programmable peripheral control device for controlling peripherals of a computer system |
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Simultaneous dual-energy computer assisted tomography
| Details |
Inventors: Brooks, Rodney A.;
Assignee: The United States of America as represented by the Department of Health, (Washington, DC)
Primary Examiner: Church; Craig E.
Assistant Examiner:
Attorney, Agent or Firm: Browdy and Neimark
A dual-energy detector system for use in computer assisted tomography. This system produces two independent sets of information from one scan, namely, high-energy and low-energy data. The system employs two cooperating detectors. The first one responds primarily to low-energy photons, allowing most high-energy photons to pass through. The second detector lies behind the first and detects the remaining photons. Thus, two electrical signals are generated which contain information in two different energy ranges, which signals can be computer-processed. The attenuation coefficients at these two energies are sufficiently different so that differential diagnosis and chemical identification may be aided. The computer-processed signals may be employed to provide any of (a) beam-hardening correction, (b) chemical identification and composition of tissues, such as lesions, bone, etc., (c) localization of injected contrast material, or (d) attenuation coefficients for radiation therapy planning. |
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DETAILED DESCRIPTION The present invention aims to accomplish the same purpose as the previously developed dual-kVp system by the use of a split-detector array.
The advantage of the split-detector system is that only one scan is required, with consequent elimination of the image registration problem.
The system also provides somewhat better energy separation than the previous method using 100 kVp and 140 kVp.
Other possible applications are the elimination of the need for a "precontrast" scan before injecting iodinated contrast material, and the prediction of attenuation coefficients in radiation therapy.
Finally, and possibly most importantly, the system may be used to implement a suggestion of Alvarez and Macoviski (6) for correcting the raw data in order to eliminate beam-hardening artifacts.
The split-detector technique* requires two detectors back-to-back in the path of the X-ray beam.
The first detector captures mostly low-energy photons while the second detector captures the remaining high-energy photons.
The method may be implemented using scintillation, gas ionization, or other types of detectors.
*See (A) Brooks et al, "Split-Detector Computed Tomography: A Preliminary Report", Radiology, Vol.
126, No.
1, pp.
255-257 (Jan.
1978); and (B) R.
A.
Brooks, "A Quantitative Theory of the Hounsfield Unit and its Application to Dual-Energy Scanning", J.
Comput.
Assist.
Tomog.
, 1 (4):487-493, Oct.
1977; both (A) and (B) are hereby incorporated by reference.
Accordingly, objects of the invention are to provide for improved tomography; to overcome deficiencies in the prior art, such as those noted above, e.
g.
to provide an improved dual-energy computer assisted tomography system which overcomes the deficiencies and disadvantages of the previously known dual-energy techniques.
A further object of the invention is to provide an improved dual-energy computer assisted tomography system which can obtain dual-energy slice data using only one scan, thereby avoiding registration problems arising with two scans
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I/O Systems 
