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US 5,724,037 AGranted
Data acquisition system for computed tomography scanning and related applications
AssigneeAnalog Devices, Inc.
InventorWai L. Lee
Life of this patent
Estimating the term…
Abstract
A computed tomography imaging method includes receiving an analog beam intensity signal from a computed tomography scanner and converting the signal into a series of digital representations of the signal at successive points in time using a predetermined sample rate. Indications that a portion of the scanner has reached a certain position relative to the beam are received asynchronously with respect to the sample rate. The value of at least one of the digital representations is adjusted in response to the indications to obtain a corrected digital representation of the analog signal.
Claims37
A computed tomography scanning system, comprising:
- an x-ray source,
- a plurality of x-ray detectors positioned to receive x-rays from the x-ray source,
- a position sensor responsive to a position of the x-ray source relative to the x-ray detectors,
- a plurality of sigma-delta modulators each having an input operatively connected to an output of one of the x-ray detectors,
- a plurality of decimator portions each having a modulated detector signal input operatively connected to an output of one of the modulators, the decimator portions each having a convert signal input operatively connected to an output of the position sensor and having a clock signal input, wherein the decimator portions are each responsive to a convert signal on the convert signal input to define a decimation period during which each decimator decimates a modulated detector signal on the modulated detector signal input based on a clock signal on the clock line,
- a digital signal processing stage responsive to outputs of the decimator portions, and having a display output, and a display responsive to the digital signal processing stage.
3 more elements
The apparatus of claim 6 wherein the coefficient source includes a read-only memory having a data output operatively connected to the coefficient source output.
A computed tomography imaging method, comprising:
- receiving an analog beam intensity signal from a computed tomography scanner,
- converting the analog beam intensity signal into a series of digital representations of the analog beam intensity signal at successive points in time using a predetermined sample rate,
- receiving at particular points in time indications that a portion of the scanner has reached a certain position relative to the beam, the indications being received asynchronously with respect to the sample rate, and
- adjusting the value of at least one of the digital representations in response to the indications to obtain a corrected digital representation of the analog signal at that particular point in time.
1 more element
An analog-to-digital converter, comprising:
- a sigma-delta modulator,
- a convert signal line,
- a decimator having a data input operatively connected to an output of the modulator and a control input operatively connected to the convert signal line, the decimator having a variable decimation ratio timed by a signal on the convert signal line on a sample-by-sample basis, and
- a decimation period timer operatively connected to the convert signal line.
1 more element
A computed tomography scanning system, comprising:
- an x-ray source,
- a plurality of x-ray detectors positioned to receive x-rays from the x-ray source,
- a plurality of sigma-delta modulators each being responsive to one of the x-ray detectors,
- a convert signal line,
- a plurality of decimators each having a data input operatively connected to an output of one of the modulators and a control input operatively connected to the convert signal line, the modulators having a variable decimation ratio timed by a signal on the convert signal line on a sample-by-sample basis,
- a decimation period timer operatively connected to the convert signal line,
- a digital signal processing stage responsive to the output of the decimators and the decimation period timer, and having a display output, and
- a display responsive to the digital signal processing stage.
5 more elements
A computed tomography imaging method, comprising:
- sigma-delta modulating an analog beam intensity signal to obtain a modulated version of the analog beam intensity signal, and
- decimating the modulated version of the analog beam intensity signal according to a variable-length rectangular time domain response with significantly rounded rising and falling ends, wherein the period between the rounded ends is variable on a sample-by-sample basis, and wherein the ends are rounded such that substantially all high frequency quantization noise from the modulator is removed.
An analog-to-digital converter, comprising:
- a transimpedance amplifier having a current input, an amplified voltage output, and a power supply input responsive to a first power supply voltage, wherein the transimpedance amplifier includes an operational amplifier coupled with a feedback resistor of above at least 10 megaohms in resistance,
- a sigma-delta conversion circuit having an input responsive to the output of the transimpedance amplifier, and a power supply input responsive to a second power supply voltage, the first power supply voltage being higher than the second power supply voltage, and
- a voltage divider connected in a signal path between the amplified output of the amplifier and the input of the circuit.
A computed tomography scanning system, comprising:
- an x-ray source,
- a plurality of x-ray detectors positioned to receive x-rays from the x-ray source,
- a plurality of analog-to-digital converters each comprising:
- a transimpedance amplifier having a current input, an amplified voltage output, and a power supply input responsive to a first power supply voltage, the current input of the transimpedance amplifier of each of the analog-to-digital converters being responsive to one of the detectors, the transimpedance amplifiers each an operational amplifier coupled with a feedback resistor of above at least 10 megaohms in resistance,
- a modulator having an analog input responsive to the output of its respective amplifier, a power supply input responsive to a second power supply voltage, the first power supply voltage being higher than the second power supply voltage, and
- a digital output, and
- a voltage divider connected in a signal path between the amplified voltage output of the amplifier and the input of the modulator,
- a digital signal processing stage responsive to the output of the modulators, and having a display output, and
- a display responsive to the digital signal processing stage.
6 more elements
A computed tomography scanning system, comprising:
- sensor means responsive to a position of an x-ray source relative to x-ray detectors,
- a plurality of sigma-delta modulators each having an input operatively connected to an output of one of the x-ray detectors,
- decimation means responsive to the modulators, to the sensor means, and to a clock signal, to define based on a signal from the sensor means a decimation period during which the decimator means decimate modulated detector signals from the modulators based on the clock signal,
- digital signal processing means responsive to the decimation means, and
- display means responsive to the digital signal processing means.
2 more elements
A computed tomography scanning system, comprising:
- means for sigma-delta modulating an analog beam intensity signal to obtain a modulated version of the analog beam intensity signal, and
- means for decimating the modulated version of the analog beam intensity signal according to a variable-length rectangular time domain response with significantly rounded rising and falling ends, wherein the period between the rounded ends is variable on a sample-by-sample basis, and wherein the ends are rounded such that substantially all high frequency quantization noise from the modulator is removed.
Dependencies are inferred from the claim text.