Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-11
2001-07-24
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S481000, C600S483000, C600S508000, C600S509000, C600S513000, C600S521000, C600S546000, C378S021000, C378S062000, C378S145000, C378S146000, C378S150000, C378S162000
Reexamination Certificate
active
06266553
ABSTRACT:
SPECIFICATION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a computed tomography apparatus operable in a spiral scanning mode for obtaining an image of a patient's heart, as well as to a method for operating such a computed tomography apparatus for obtaining cardiac images.
2. Description of the Prior Art
It is known to conduct helical or spiral scanning of a patient, using a computed tomography apparatus, by causing the measurement unit consisting of the X-ray source and the detector to continuously rotate while displacing the patient bed along its longitudinal direction (z-direction). From the detector data, volume data of the subject of examination can be obtained using an image computer.
Movements of the organs, in particular of the heart, can lead to motion artifacts in the image produced from the volume data, due to the relatively long scan time.
U.S. Pat. No. 4,182,311 describes a method for computed tomography of the heart which does not make use of spiral scanning. In parallel with the scanning of the heart, the ECG signal is recorded. On the basis of the ECG signal, those projections are selected that correspond to a particular phase of the heart action. These projections, associated with various projection angles, are combined to form a dataset that allows the reconstruction of an image.
In U.S. Pat. No. 5,383,231 a method is described for spiral scanning of the heart by means of a computed tomography apparatus, in which, in a manner analogous to the method of U.S. Pat. No. 4,182,311, projections associated with various projection angles and/or various revolutions of the measurement system, and which reproduce the same phase of the heart action, are combined to form datasets that allow the reconstruction of CT images, in particular three-dimensional CT images.
In both cases, an improvement is achieved in comparison to tomographic examinations of the heart that take place without taking into account the ECG signal; however, sufficiently sharp images still are not produced.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a computed tomography apparatus which is operable in a spiral scanning mode wherein a sharp imaging of the heart is achieved.
The above object is achieved in accordance with the principles of the present invention in a computed tomography apparatus having a measurement system for conducting a spiral scan of a measurement volume containing a patient's heart, wherein the production of scanning data obtained using the spiral scanning is synchronized with an ECG signal from the patient in order to produce a graphic representation of the examination volume, and thus an image of the patient's heart.
The ECG signal is not merely used as a periodic trigger, as is conventional in the above-described known systems, but instead is employed to control the generation of volumetric data during the spiral scanning at phases of the cardiac cycle wherein minimum movement of the heart takes place, i.e., in the diastole. The chronological correlation between the recording of the scanning data in the spiral scanning an ECG signal is fixed, such as by employing the “radiation on” signal for conducting the spiral scanning, so that within each of a number of successive time intervals, a dataset is obtained completely within that time interval, with the datasets from the successive time intervals then being combined to produce a low-motion image of the heart. Since all of the scanning data are obtained at times when the heart is in a low-motion phase, the resulting complete image is particularly sharp, in contrast to images produced employing conventional ECG triggering.
REFERENCES:
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patent: 4547892 (1985-10-01), Richey et al.
patent: 4868747 (1989-09-01), Mori et al.
patent: 5262946 (1993-11-01), Heuscher
patent: 5383231 (1995-01-01), Yamagishi
patent: 5800355 (1998-09-01), Hasegawa
Fluhrer Manfred
Klingenbeck-Regn Klaus
Lutz Andreas
Regn Judith
Lateef Marvin M.
Lin Jeoyuh
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
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