Modulating X-ray radiation dose in CT scan

Patent metadata

Field	Value
Publication number	US-9877695-B2
Application number	US-201514945441-A
Country	US
Kind code	B2
Filing date	Nov 19, 2015
Priority date	Nov 19, 2014
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

A method for modulating x-ray radiation dose in CT scan is disclosed. The method may include: acquiring x-ray attenuation information of each Z position within a planned scanning sequence for a scan region of a subject from data of a finished scanning sequence for the subject; and then, based on the acquired x-ray attenuation information, performing dose modulation with respect to the XY scanning profile at each Z position within the planned scanning sequence. The finished scanning sequence can be an axial and/or helical scanning sequence for a scan region wholly or partially same as the scan region and has been performed earlier. The Z position may include a position in Z direction extending from head to foot of the subject or conversely. The XY scanning profile may include a scanning profile of the subject which is vertical to Z direction.

First claim

The invention claimed is:

1. A method for modulating x-ray radiation dose in CT scan, the method comprising:
acquiring, from data of a finished scanning sequence of a subject, x-ray attenuation information for each of the projection angles of the XY scanning profile at each of Z positions within a planned scanning sequence of the subject; and
modulating, according to the acquired x-ray attenuation information, an x-ray radiation dose for each of the projection angles of the XY scanning profile at each of Z positions within the planned scanning sequence;
wherein Z position includes a position in Z direction from head to foot of the subject or conversely, the XY scanning profile represents a profile of the subject which is vertical to Z direction and the finished scanning sequence of the subject includes a scanning sequence for a same scan region of the same subject which has been finished before current time;
wherein when the planned scanning sequence goes beyond the finished scanning sequence and pilot image data of the planned scanning sequence has no abrupt change in Z direction, the method further includes:
acquiring shape ratio information of the XY scanning profile at each of Z positions in an overlapping sequence, wherein the overlapping sequence is a part of the planned scanning sequence which is overlapped with the finished scanning sequence, and
determining whether the XY scanning profiles at different Z positions within the overlapping sequence are similar to each other based on the acquired shape ratio information,
when the XY scanning profiles at different Z positions within the overlapping sequence are determined as being similar to each other, modulating the x-ray radiation dose for each of the projection angles of the XY scanning profile at each of Z positions within the planned scanning sequence according to the acquired x-ray attenuation information.

2. The method of claim 1 , wherein, when the planned scanning sequence is within the finished scanning sequence:
said acquiring the x-ray attenuation information for each of the projection angles of the XY scanning profile at each of Z positions within the planned scanning sequence includes: acquiring, from the data of the finished scanning sequence, a maximum x-ray attenuation value for each of the projection angles at each of Z positions within the planned scanning sequence, and
said modulating the x-ray radiation dose for each of the projection angles of the XY scanning profile at each of Z positions within the planned scanning sequence includes: calculating the x-ray radiation dose for each of the projection angles of the XY scanning profile at each of Z positions zi within the planned scanning sequence with the following equation:

I

mod
,
zi
,
j

=

M
·

I

mod
,
zi
,
start

∑

j
=
1

M

⁢

A

max
,
zi
,
j

·

A

max
,
zi
,
j

;

wherein, I mod,zi,j represents an x-ray radiation dose for the j th projection angle of the XY scanning profile at Z position zi,
I mod,zi,start represents an initial x-ray radiation dose of Z position zi,
M represents a quantity of projection angles, and j represents an index number of the j th projection angle, and
A max,zi,j represents a maximum x-ray attenuation value for the j th projection angle of the XY scanning profile at Z position zi and is acquired from the data of the finished scanning sequence.

3. The method of claim 1 , said acquiring the x-ray attenuation information for each of the projection angles of the XY scanning profile at each of Z positions within the planned scanning sequence, includes:
acquiring a maximum x-ray attenuation value for each of the projection angles of the XY scanning profile at each of Z positions within the overlapping sequence from the data of the finished scanning sequence; and
calculating a maximum x-ray attenuation value for each of the projection angles of the XY scanning profile at each of Z positions zout within the planned scanning sequence but not in the overlapping sequence according to the following equation:

A

max
,
zout
,
j

=

A

max
,

zout
-
1

,
j

⁢

PA

max
,
zout

PA

max
,

zout
-
1

wherein, A max,zout,j represents a maximum x-ray attenuation value for the j th projection angle of the XY scanning profile at Z position zout;
A max,zout−1,j represents a maximum x-ray attenuation value for the j th projection angle of the XY scanning profile at Z position zout−1 which is closest to the Z position zout;
PA max,zout represents a maximum x-ray attenuation value in pilot image scanning of the XY scanning profile at Z position zout and is determined from a pre-acquired pilot image data of the subject; and
PA max,zout−1 represents a maximum x-ray attenuation value in pilot image scanning of the XY scanning profile at Z position zout−1 and is determined from pre-acquired pilot image data of the subject.

4. The method of claim 3 , wherein, said modulating the x-ray radiation dose for each of the projection angles of the XY s

Assignees

• Shenyang Neusoft Medical Sys

Inventors

• Lou Shanshan
• Ren Liang
• Pang Ling

Classifications

• A61B6/583

  using calibration phantoms · CPC title

• A61B6/032

  Transmission computed tomography [CT] · CPC title

• A61B6/544 Primary

  dependent on patient size · CPC title

• A61B6/488

  involving pre-scan acquisition · CPC title