Modulation of X-ray tube current during CT scanning
AssigneeGeneral Electric Company
InventorsKenneth R. Williams, Herbert K. Koehl, Jonathan R. Schmidt
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Abstract
An x-ray CT system modulates x-ray tube current as a function of gantry angle to reduce the total patient dose without significantly increasing image noise. A modulation waveform is stored in a table as a function of gantry angle, and during a slice acquisition, values are periodically read from this table and employed to calculate tube current commands. Tube current is monitored and compared with the latest command to ensure the proper x-ray dose is applied.
Claims6
A method for modulating the dose of an x-ray beam applied to a patient by an x-ray CT system during a scan, the steps comprising:
- calculating a command mA.sub.max which determines the maximum dose of the x-ray beam;
- storing a waveform table indicative of the desired modulation as a function of an x-ray CT system gantry angle;
- periodically during the scan calculating an mA command which controls the dose of the x-ray beam by:
- a) determining the current x-ray CT system gantry angle;
- b) reading a value from the stored waveform using the x-ray CT system gantry angle as an index into the waveform table;
- and
- c) multiplying the command mA.sub.max by the value read from the waveform table;
- and
- outputting the calculated mA command to an x-ray controller which controls the dose of the x-ray beam.
Dependencies are inferred from the claim text.