Methods and apparatus for truncation compensation
AssigneeGE Medical Systems Global Technology Company, LLC
InventorsJiang Hsieh, Brian Grekowicz, Edward Henry Chao, Scott Matt McOlash, Amy Lynn Horst
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Abstract
A method includes calculating a sum of all samples at each projection view of a scan of an object, determining a maximum value of the calculated sums, averaging a plurality of samples m at a projection view index k when the sum of all samples at index k is less than a predetermined percentage of the maximum value, comparing the average to a threshold t, determining the projection truncated when the average is greater than t, and determining the projection not truncated when the average is not greater than t.
Claims27
A method for determining whether a projection is truncated, said method comprising:
- calculating a sum of all samples at each projection view of a scan of an object;
- determining a maximum value of the calculated sums;
- averaging a plurality of samples m at a projection view index k when the sum of all samples at index k is less than a predetermined percentage of the maximum value;
- comparing the average to a threshold t;
- determining the projection truncated when the average is greater than t;
- and
- determining the projection not truncated when the average is not greater than t.
An imaging apparatus comprising:
- a radiation source;
- a detector responsive to radiation positioned to receive radiation emitted from said source;
- and
- a computer operationally coupled to said radiation source and said detector, said computer configured to:
- calculate a sum of all samples at each projection view of a scan of an object;
- determine a maximum value of the calculated sums;
- average a plurality of samples m at a projection view index k when the sum of all samples at index k is less than a predetermined percentage of the maximum value;
- compare the average to a threshold t;
- determine the projection truncated when the average is greater than t;
- and
- determine the projection not truncated when the average is not greater than t.
A computer readable medium encoded with a program configured to instruct a computer to:
- calculate a sum of all samples at each projection view of a scan of an object;
- determine a maximum value of the calculated sums;
- average a plurality of samples m at a projection view index k when the sum of all samples at index k is less than a predetermined percentage of the maximum value;
- compare the average to a threshold t;
- determine the projection truncated when the average is greater than t;
- determine the projection not truncated when the average is not greater than
- estimate a total attenuation τ(k) in accordance with
- τ
-
- (
- k
- )
- =
- k
- 2
- -
- k
- k
- 2
- -
- k
- 1
-
- ξ
-
- (
- k
- 1
- )
- +
- k
- -
- k
- 1
- k
- 2
- -
- k
- 1
-
- ξ
-
- (
- k
- 2
- )
- where k1 and k2 are averages of a plurality of view locations of un-truncated views adjacent to a truncation region comprising at least one projection
- determined truncated, and ξ(k) is calculated as
- ξ
-
- (
- k
- )
- =
- ∑
- i
- =
- 1
- N
-
- p
-
- (
- i
- ,
- k
- )
- ;
- determine a attenuation difference λ(k) in accordance with λ(k)=τ(k)−ξ(k);
- calculate an amount of attenuation to add η(k) in accordance with
- η
-
- (
- k
- )
- =
- π
- 2
-
- R
- l
- 2
-
- (
- k
- )
- -
- x
- l
-
- (
- k
- )
-
- p
- l
-
- (
- k
- )
- -
- R
- l
- 2
-
- (
- k
- )
-
- arcsin
-
- (
- x
- l
-
- (
- k
- )
- R
- l
-
- (
- k
- )
- )
- +
- π
- 2
-
- R
- r
- 2
-
- (
- k
- )
- -
- x
- r
-
- (
- k
- )
-
- p
- r
-
- (
- k
- )
- -
- R
- r
- 2
-
- arcsin
-
- (
- x
- r
-
- (
- k
- )
- R
- r
-
- (
- k
- )
- )
- where p1(k), and pr(k), are the magnitude of a left and a right projection boundary samples averaged over multiple views, respectively, and x1(k), xr(k), R1(k), and Rr(k) are a location and radius of a left and right fitted cylinders, respectfully;
- compare η(k) to λ(k) by calculating a ratio
- ɛ
-
- (
- k
- )
- =
- η
-
- (
- k
- )
-
- μ
- w
- λ
-
- (
- k
- )
- where μw is an attenuation coefficient of water,
- compare ε(k) to a threshold q;
- use at least one of η(k) and λ(k) to correct an image when ε(k) is not greater than q;
- and
- when ε(k) is greater than q:
- calculate a ηn(k) based on data regarding a k1−n view and a k2+n view, wherein n is an integer;
- and
- correct an image using the ηn(k).
Dependencies are inferred from the claim text.