US 8,787,646 B2Granted

Method and apparatus for computed tomography image reconstruction

AssigneeKoninklijke Philips N.V.

InventorsDirk Schaefer, Michael Grass

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Abstract

A method and apparatus are provided to reconstruct projection data obtained from CT imaging devices with offset detector geometries. According to one aspect of the present invention, a method is provided to reconstruct projection data obtained from CT imaging devices with offset detector geometries that includes the following steps: (i) matching projection data measured at opposing sides of the acquisition trajectory and splicing them together to generate a full, non-truncated projection data set; (ii) differentiation of the projection data; (iii) filtering the differentiated projection data with a filter, such as for example a Hilbert filter; (iv) applying redundancy weighting to the filtered projection data; and (v) back-projecting the redundancy weighted projection data to generate image data.

Claims23

Dependent claims

An imaging method, comprising the steps of:

acquiring projection data of an object with an imaging apparatus comprising a detector which is offset from a center of rotation;
matching at least one first projection from the projection data with at least one second projection from the projection data, wherein the at least one second projection is measured at an approximately opposing side of an acquisition trajectory from the at least one first projection;
splicing estimated projection data derived from the projection data of the at least one second projection with projection data of the first projection to generate a full, non-truncated projection data set;
differentiating the non-truncated projection data set with respect to the acquisition trajectory to generate differentiated projection data;
applying a filter to the differentiated projection data to generate differentiated and filtered projection data;
applying redundancy weighting to the differentiated and filtered projection data to generate differentiated, filtered and weighted projection data;
and
back-projecting the differentiated, filtered and weighted projection data to generate volumetric data indicative of the object;
wherein the at least one second projection is selected in a region μmin≦μ≦μ−0 with μmin=−μmax according to {tilde over (X)}1(α,ν,β)={tilde over (X)}(−α,ν,β+2α+π) for α(μmin)≦α≦α(μ−0);
and
wherein {tilde over (X)}(α,ν,β)=X(atan(μ/D),ν,λ/R), D is a distance from a source to the detector, R is a distance from the source to a rotation axis, a circular orbit is parameterized by a path length λεΛ=[0, 2πR), a detector ν-axis is parallel to the rotational axis, and a u-axis is parallel to a trajectory tangent vector.

8 more elements

An apparatus for acquiring projection data at a plurality of angular positions relative to an object disposed in an examination region, the apparatus comprising:

a radiation source;
a radiation sensitive detector which detects radiation emitted by the source that has traversed the examination region, wherein the detector is offset from a center of rotation;
and
a reconstructor;
wherein the apparatus is adapted to perform a scanning procedure of the object to obtain projection data;
wherein at least one first projection from the projection data is matched with at least one second projection from the projection data, wherein the at least one second projection is measured at an approximately opposing side of an acquisition trajectory from the at least one first projection;
wherein projection data from the at least one second projection is used to derive estimated projection data that is spliced with projection data of the first projection to generate a full, non-truncated projection data set;
wherein the full, non-truncated projection data set is then differentiated with respect to the acquisition trajectory to generate differentiated projection data;
wherein the differentiated projection data is then filtered to generate differentiated and filtered projection data;
wherein redundancy weighting is applied to the differentiated and filtered projection data to generate differentiated, filtered and weighted projection data;
wherein the differentiated, filtered and weighted projection data is then back-projected by the reconstructor to generate volumetric data indicative of the object;
and
wherein the at least one second projection is selected in a region μmin≦μ≦μ−0 with μmin=−μmax according to {tilde over (X)}1(α,ν,β)={acute over (X)}(−α,ν,β+2α+π) for α(μmin)≦α≦α(μ−0);
and
wherein {acute over (X)}(α,ν,β)=X(atan(μ/D),ν,λ/R), D is a distance from a source to the detector, R is a distance from the source to a rotation axis, a circular orbit is parameterized by a path length λεΛ=[0, 2πR), a detector v-axis is parallel to the rotational axis, and a μ-axis is parallel to a trajectory tangent vector.

12 more elements

An imaging method, comprising the steps of:

acquiring projection data of an object with an imaging apparatus comprising a detector which is offset from a center of rotation;
matching at least one first projection from the projection data with at least one second projection from the projection data, wherein the at least one second projection is measured at an approximately opposing side of an acquisition trajectory from the at least one first projection;
splicing estimated projection data derived from the projection data of the at least one second projection with projection data of the first projection to generate a full, non-truncated projection data set;
differentiating the non-truncated projection data set with respect to the acquisition trajectory to generate differentiated projection data;
applying a filter to the differentiated projection data to generate differentiated and filtered projection data;
applying redundancy weighting to the differentiated and filtered projection data to generate differentiated, filtered and weighted projection data;
and
back-projecting the differentiated, filtered and weighted projection data to generate volumetric data indicative of the object;
wherein the imaging method comprises a reconstruction algorithm according to:
f
new
⁡
(
x
)
=
1
2
⁢
⁢
π
⁢
∫
Λ
⁢
ω
⁡
(
u
)
R
-
(
x
-
I
)
·
d
^
⁢
∫
-
∞
∞
⁢
D
SE
_
⁡
(
x
)
X
d
⁡
(
u
′
,
υ
,
λ
)
⁢
h
H
⁡
(
u
-
u
′
)
⁢
ⅆ
u
′
⁡
(
1
/
R
)
⁢
d
⁢
⁢
λ
,
with
h
H
⁡
(
ρ
)
=
-
∫
-
∞
∞
⁢
i
⁢
sgn
⁡
(
P
)
⁢
ⅇ
j
⁢
2
⁢
⁢
πρ
⁢
⁢
P
⁢
ⅆ
P
,
and
X
d
⁡
(
u
,
υ
,
λ
)
=
(
∂
χ
2
∂
λ
+
∂
χ
2
∂
u
⁢
∂
u
∂
λ
+
∂
χ
2
∂
υ
⁢
∂
υ
∂
λ
)
⁢
(
u
,
υ
,
λ
)
;
wherein D is a distance from a source to the detector, R is a distance from the source to a rotation axis, a circular orbit is parameterized by a path length λεΛ=[0, 2πR), a detector ν-axis is parallel to the rotational axis, a μ-axis is parallel to a trajectory tangent vector, I is an iso-center of the imaging apparatus, the detector center is offset from the center of rotation in a transaxial plane by a distance d, and SE is a length from the source to a detector element.

174 more elements

An apparatus for acquiring projection data at a plurality of angular positions relative to an object disposed in an examination region, the apparatus comprising:

a radiation source;
a radiation sensitive detector which detects radiation emitted by the source that has traversed the examination region, wherein the detector is offset from a center of rotation;
and
a reconstructor;
wherein the apparatus is adapted to perform a scanning procedure of the object to obtain projection data;
wherein at least one first projection from the projection data is matched with at least one second projection from the projection data, wherein the at least one second projection is measured at an approximately opposing side of an acquisition trajectory from the at least one first projection;
wherein projection data from the at least one second projection is used to derive estimated projection data that is spliced with projection data of the first projection to generate a full, non-truncated projection data set;
wherein the full, non-truncated projection data set is then differentiated with respect to the acquisition trajectory to generate differentiated projection data;
wherein the differentiated projection data is then filtered to generate differentiated and filtered projection data;
wherein redundancy weighting is applied to the differentiated and filtered projection data to generate differentiated, filtered and weighted projection data;
wherein the differentiated, filtered and weighted projection data is then back-projected by the reconstructor to generate volumetric data indicative of the object;
and
wherein the reconstructor applies a reconstruction algorithm according to:
f
new
⁡
(
x
)
=
1
2
⁢
π
⁢
∫
Λ
⁢
ω
⁡
(
u
)
R
-
(
x
-
I
)
·
d
^
⁢
⁢
∫
-
∞
∞
⁢
D
SE
_
⁡
(
x
)
⁢
⁢
X
d
⁡
(
u
′
,
υ
,
λ
)
⁢
h
H
⁡
(
u
-
u
′
)
⁢
ⅆ
u
′
⁡
(
1
/
R
)
⁢
ⅆ
λ
,
⁢
with
h
H
⁡
(
ρ
)
=
-
∫
-
∞
∞
⁢
i
⁢
⁢
sgn
(
P
)
⁢
ⅇ
j2πρ
⁢
⁢
P
⁢
ⅆ
P
,
and
X
d
⁡
(
u
,
υ
,
λ
)
=
(
∂
χ
2
∂
λ
+
∂
χ
2
∂
u
⁢
∂
u
∂
λ
+
∂
χ
2
∂
υ
⁢
∂
υ
∂
λ
)
⁢
(
u
,
υ
,
λ
)
;
and
wherein D is a distance from the source to the detector, R is a distance from the source to a rotation axis, a circular orbit is parameterized by a path length λεΛ=[0, 2πR), a detector ν-axis is parallel to the rotational axis, a μ-axis is parallel to a trajectory tangent vector, I is an iso-center of the imaging apparatus, the detector center is offset from the center of rotation in a transaxial plane by a distance d, and SE is a length from the source to a detector element.

175 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/254,001Filed 18 Feb 2010 · us provisional application
Priority: 26 Mar 2009
Published: US 2012/0014582 A119 Jan 2012
Granted: 22 Jul 2014
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G06T 12/10
Tomographic reconstruction from projections: image preprocessing, e.g. calibration, positioning of sources or scatter correction
A61B 6/032
Computed tomography [CT]: transmission computed tomography [CT]
A61B 6/027
Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis: characterised by the use of a particular data…
G06T
Image data processing or generation, in general

Family

Application61/163,489Us provisional application · filed 26 Mar 2009
US 2012/0014582 A1Pre-grant publication · published 19 Jan 2012
US 8,787,646 B2This patent

From the US filing history. Foreign family members aren’t listed.

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