Controlling X-ray dose of CT scan

Patent metadata

Field	Value
Publication number	US-10064596-B2
Application number	US-201514863467-A
Country	US
Kind code	B2
Filing date	Sep 24, 2015
Priority date	Sep 30, 2014
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

A method for controlling an X-ray dose of a CT scan includes: setting an initial X-ray dose; performing a first CT scan with the initial X-ray dose to obtain an initial scan image; setting a region of interest (ROI) in the initial scan image; calculating a subsequent X-Ray dose with image values of the ROI in the initial scan image; perform an additional CT scan with the calculated subsequent X-Ray dose to obtain an average image; before receiving an end instruction, repeating the following operations: recalculating a subsequent X-Ray dose with image values of the ROI in the average image and performing an additional CT scan with the calculated subsequent X-Ray dose to obtain a new average image; and saving the average image when receiving the end instruction.

First claim

The invention claimed is:

1. A method for controlling an X-ray dose of a CT scan, the method comprises:
setting an initial X-ray dose;
performing a first CT scan with the initial X-ray dose to obtain an initial scan image;
setting a region of interest (ROI) in the initial scan image;
calculating a subsequent X-Ray dose with image values of the ROI in the initial scan image;
performing an additional CT scan with the calculated subsequent X-Ray dose to obtain an average image;
repeating the following operations before receiving an end instruction: recalculating a new subsequent X-Ray dose with image values of the ROI in the average image and performing an additional CT scan with the new subsequent X-Ray dose to obtain a new average image; and
saving the new average image when receiving the end instruction;
wherein the image values of the ROI comprise a parameter reflecting image noise of the ROI in the initial scan image or the average image;
wherein calculating the subsequent X-Ray dose with image values of the ROI in the initial scan image comprises:
calculating a standard deviation of image values of the ROI in the initial scan image as an initial standard deviation;
setting a target standard deviation;
calculating a scanning factor according to the initial standard deviation and the initial X-ray dose; and
calculating the subsequent X-Ray dose with the initial standard deviation, the target standard deviation, and the scanning factor.

2. The method according to claim 1 , wherein a formula for calculating the standard deviation of image values of the ROI in the initial scan image as the initial standard deviation is:

σ
ori

=

σ
=

1
N

⁢

∑

i
=
1

N

⁢

(

x
i

-

x
_

)

2

;

wherein, the σ ori is the initial standard deviation;
the σ is the standard deviation of image values of the ROI in the initial scan image;
the N is a number of pixels in the ROI in the initial scan image;
the x i is an image value of the i th pixel in the ROI in the initial scan image; and
the x is an average image value of pixels in the ROI in the initial scan image.

3. The method according to claim 1 , wherein a formula for calculating the scanning factor according to the initial standard deviation and the initial X-ray dose is:
σ ori 2 =D/R ori ;

where, the σ ori is the initial standard deviation,
the D is the scanning factor, and
the R ori is the initial X-ray dose.

4. The method according to claim 1 , wherein a formula for calculating the subsequent X-Ray dose with the initial standard deviation, the standard deviation, and the scanning factor is:

R
′

=

{

D

4
⁢

σ
obj
2

-

σ
ori
2

,

4
⁢

σ
obj
2

-

σ
ori
2

>
0

D

σ
ori
2

,

4
⁢

σ
obj
2

-

σ
ori
2

≤
0

;

where, the R′ is the subsequent X-Ray dose,
the D is the scanning factor,
the σ obj is the target standard deviation, and
the σ ori is the initial standard deviation.

5. The method according to claim 1 , wherein setting the target standard deviation comprises:
setting the target standard deviation as 1/K of the initial standard deviation, wherein the K is an integer greater than or equal to 2.

6. The method according to claim 1 , wherein recalculating the new subsequent X-Ray dose with image values of the ROI in the average image comprises:
calculating a standard deviation of image values of the ROI in the average image as a current standard deviation; and
calculating the new subsequent X-Ray dose with the current standard deviation, the scanning

Assignees

• Shenyang Neusoft Medical Sys

Inventors

• Lou Shanshan
• Fang Gang
• Zhao Jiangwei

Classifications

• A61B6/40

  Arrangements for generating radiation specially adapted for radiation diagnosis · CPC title

• A61B6/545 Primary

  involving automatic set-up of acquisition parameters · CPC title

• A61B6/52

  Devices using data or image processing specially adapted for radiation diagnosis · CPC title

• A61B6/4085

  Cone-beams · CPC title

• A61B6/032

  Transmission computed tomography [CT] · CPC title