US 7,689,055 B2Granted

Method and apparatus for enhancing image acquired by radiographic system

AssigneesNuctech Company Limited, Tsinghua University

InventorsLi Zhang, Zhiqiang Chen, Yuxiang Xing, Yuanjing Li, Yinong Liu, Ziran Zhao, Yongshun Xiao

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Abstract

A method of image information enhancement in radiography relates to image information processing techniques in radiography. The method comprising steps of: normalizing an acquired image A(x,y) to form a normalized image B(x,y); filtering the normalized image B(x,y) by a low-pass filter to obtain an filtered image C(x,y); calculating a relative standard deviation for each pixel in the image A(x,y), three times the relative standard deviation being an edge threshold for each pixel; thresholding a difference image obtained by subtracting the filtered image C(x,y) from the normalized image B(x,y) by using the edge threshold for each pixel to form a threshold-processed image D(x,y); enhancing a contrast of the threshold-processed image D(x,y) by using a non-linear function to form a contrast-enhanced image E(x,y); determining a enhancement coefficient a(x,y); obtaining a edge-enhanced image F(x,y) by multiplying the enhancement coefficient a(x,y), the contrast-enhanced image E(x,y) and the filtered image C(x,y); and generating a resulting image by multiplying a sum of the edge-enhanced image F(x,y) and the filtered image C(x,y) with the maximum value Amax As compared with the prior arts, the inventive method has a fast processing speed for image information enhancement and a simple algorithm, images clearly, eliminates noises in the images, and satisfies the requirements of relatively more enhancement to the contrast of the dark regions in the scanned images.

Claims5

Dependent claims

A method for operating a radiographic system comprising the steps of:

emitting from X-rays which penetrate through an object to be detected being carried by a mechanical control device;
receiving by a detector device the X rays and transmitting the received signal from the detector device to a data acquisition device;
converting the signal into a digital signal and transferring the digital signal to a computer imaging device;
the method further comprising the steps of, at the computer imaging device;
normalizing an acquired image A(x,y) to form a normalized image B(x,y);
filtering the normalized image B(x,y) by a low-pass filter to obtain an filtered image C(x,y);
calculating a relative standard deviation for each pixel in the image A(x,y), three times the relative standard deviation being an edge threshold for each pixel, wherein the relative standard deviation is calculated as below:
σ
⁡
(
x
,
y
)
=
{
∑
i
,
j
=
-
N
2
N
2
⁢
[
A
⁡
(
x
i
,
y
j
)
-
M
⁡
(
x
,
y
)
]
2
}
/
(
N
2
-
1
)
wherein M(x,y) is an average value of pixel neighborhood for pixel (x,y), and N denotes a width of pixel neighborhood;
subtracting the filtered image C(x,y) from the normalized image B(x,y) to obtained a difference image;
thresholding the difference image using the edge threshold for each pixel to form a threshold-processed image D(x,y);
enhancing a contrast of the threshold-processed image D(x,y) by using a non-linear function to form a contrast-enhanced image E(x,y), wherein the non-linear function is arranged to implement a sine transformation;
determining a enhancement coefficient a(x,y) for each pixel as below:
α
⁡
(
x
,
y
)
=
c
A
⁡
(
x
,
y
)
A
max
,
wherein c is a predetermined constant, Amax is the maximum value of pixel in the image A(x,y);
obtaining a edge-enhanced image F(x,y) by multiplying the enhancement coefficient a(x,y), the contrast-enhanced image E(x,y) and the filtered image C(x,y), and
generating a resulting image by multiplying a sum of the edge-enhanced image F(x,y) and the filtered image C(x,y) with the maximum value Amax.

79 more elements

A radiographic system comprising:

a radiation source, a mechanical control device, a detector device, a data acquisition device and computer imaging device, the radiation source emits X rays which penetrate through an object to be detected being carried by the mechanical control device, and then are received by the detector device facing the X rays, the received X rays signal is transmitted from the detector device to the data acquisition device, and after being converted into a digital signal, is transferred to the computer imaging device, the computer imaging device being arranged to:
normalize an acquired image A(x,y) to form a normalized image B(x,y);
filter the normalized image B(x,y) by a low-pass-filter to obtain an filtered image C(x,y);
calculate a relative standard deviation for each pixel in the image A(x,y), three times the relative standard deviation being an edge threshold for each pixel, wherein the relative standard deviation is calculated as below:
σ
⁡
(
x
,
y
)
=
{
∑
i
,
j
=
-
N
2
N
2
⁢
⁢
[
A
⁡
(
x
i
,
y
j
)
-
M
⁡
(
x
,
y
)
]
2
}
/
(
N
2
-
1
)
wherein M (x,y) is an average value of pixel neighborhood for a pixel (x,y), N denotes a width of pixel neighborhood;
subtract the filtered image C(x,y) from the normalized image B(x,y) to obtained a difference image;
threshold a difference image by using the edge threshold for each pixel to form a threshold-processed image D(x,y);
enhance a contrast of the threshold-processed image D(x,y) by using a non-linear function to form a contrast-enhanced image E(x,y), wherein the non-linear function is arranged to implement a sine transformation;
determine a enhancement coefficient a(x,y) for each pixel as below:
α
⁡
(
x
,
y
)
=
c
A
⁡
(
x
,
y
)
A
max
,
wherein c is a predetermined constant, Amax is the maximum value of pixel in the image A(x,y);
obtain a edge-enhanced image F(x,y) by multiplying the enhancement coefficient a(x,y), the contrast-enhanced image E(x,y) and the filtered image C(x,y) and
generate a resulting image by multiplying a sum of the edge-enhanced image F(x,y) and the filtered image C(x,y) with the maximum value Amax.

77 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/472,193Filed 21 Jun 2006
Priority: CN 2005 1 007779727 Jun 2005
Published: US 2006/0291742 A128 Dec 2006
Granted: 30 Mar 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G06T 5/40
Image enhancement or restoration: using histogram techniques
G06T 5/92
Dynamic range modification of images or parts thereof: based on global image properties
G06T 2207/10116
Image acquisition modality: x-ray image
G06T 2207/30004
Subject of image; Context of image processing: biomedical image processing