Scatter correction for x-ray imaging using modulation of primary x-ray spatial spectrum
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorsLei Zhu, Rebecca Fahrig
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Abstract
Scatter radiation in an x-ray imaging system including an x-ray source and an x-ray detector is separated by using amplitude modulation to translate the spatial frequency of a detected x-ray beam to a higher frequency and provide separation from low frequency scatter signal. The low frequency content of the detected x-ray beam is then obtained by demodulating the detected modulated signal.
Claims12
In x-ray imaging, a method of spatial frequency translating a detected signal from a primary x-ray source for separation from low frequency scatter radiation signal comprising the steps of:
- a) amplitude modulating the x-ray beam from a primary x-ray source thereby creating a side band of a high-frequency primary signal with frequency equal to the sum of frequency of the modulation and frequency of the x-ray beam,
- b) detecting the side band, whereby the side band frequency is spaced from low frequency scatter radiation;
- c) estimating a low-frequency primary signal from the detected side band of the high-frequency primary signal;
- and
- d) using the estimated low-frequency primary signal to estimate scatter.
In the processing of detected x-rays from a primary X-ray source and separating the detected scatter radiation signal from a detected signal, a method comprising the steps of:
- a) amplitude modulating x-rays from a primary x-ray source,
- b) detecting amplitude modulated radiation,
- c) low pass filtering the detected signals from step b) to obtain a scatter signal and a low frequency portion of a spectrum of a detected primary signal,
- d) high pass filtering the detected signals from step b) to obtain a measure of a high frequency portion of the detected signals,
- e) demodulating the high pass filtered detected signals from step d) to obtain a measure of low frequency portion of the spatial spectrum of the detected primary signal, and
- f) subtracting a weighted measure of the low frequency portion from step e) from the low pass filtered detected signals from step c) to provide a measure of scatter radiation signal.
Apparatus for use in separating scatter radiation in an x-ray imaging system in which radiation from an x-ray source passes through an imaged object to an x-ray detector comprising:
- a) a sheet having a repetitive pattern of material with different radiation attenuation through which the radiation passes thereby amplitude modulating the radiation at a modulation frequency determined by the pattern repetition, wherein the sheet is placed between the x-ray source and the imaged object,
- b) a high pass filter for separating high frequency signals from the detector,
- c) a demodulator for shifting high frequency signals to lower frequencies, thereby providing a measure of low frequency primary signal without low frequency scatter signal.
Dependencies are inferred from the claim text.