Methods and apparatus for helical reconstruction for multislice CT scan

US 6,980,681 B1
Filed: 04/24/2000
Issued: 12/27/2005
Est. Priority Date: 04/24/2000
Status: Expired due to Fees

First Claim

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1. A method for imaging an object with a computed tomographic (CT) imaging system, comprising the steps of:

helically scanning the object with a multi-slice CT imaging system having a plurality of detector rows to acquire attenuation measurements of the object, the measurements including more than two conjugate samples, wherein a difference between a view angle of one of the more than two conjugate samples and a view angle of any one of the remaining conjugate samples of the more than two conjugate samples is n π

, wherein n is an integer greater than zero;

estimating at least one projection along a curved plane of reconstruction of the object using the attenuation measurements of the object, including the more than two conjugate samples;

applying different weighting functions within each detector row dependent upon a division of conjugate regions for each detector row and dependent upon view angles in a curved plane for corresponding detector rows; and

filtering and backprojecting the attenuation measurements of the object, including the more than two conjugate samples, to reconstruct at least one image slice of the object.

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Abstract

One embodiment of the present invention is a method for imaging an object with a computed tomographic (CT) imaging system that includes steps of helically scanning the object with a multi-slice CT imaging system to acquire attenuation measurements of the object, the measurements including more than two conjugate samples for estimation of a projection at a plane of reconstruction of the object; and filtering and backprojecting the attenuation measurements of the object, including the more than two conjugate samples, to reconstruct at least one image slice of the object. An improved sampling pattern and better use of the attenuation samples obtained during a scan is thus provided.

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30 Claims

1. A method for imaging an object with a computed tomographic (CT) imaging system, comprising the steps of:
- helically scanning the object with a multi-slice CT imaging system having a plurality of detector rows to acquire attenuation measurements of the object, the measurements including more than two conjugate samples, wherein a difference between a view angle of one of the more than two conjugate samples and a view angle of any one of the remaining conjugate samples of the more than two conjugate samples is n π
  
  , wherein n is an integer greater than zero;
  
  estimating at least one projection along a curved plane of reconstruction of the object using the attenuation measurements of the object, including the more than two conjugate samples;
  
  applying different weighting functions within each detector row dependent upon a division of conjugate regions for each detector row and dependent upon view angles in a curved plane for corresponding detector rows; and
  
  filtering and backprojecting the attenuation measurements of the object, including the more than two conjugate samples, to reconstruct at least one image slice of the object.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
- - 2. A method in accordance with claim 1 wherein the more than two conjugate samples are located within a predetermined distance from the curved plane of reconstruction of the object.
  - 3. A method in accordance with claim 1 wherein the CT imaging system has N detector rows, and further comprising the step of selecting a helical pitch P:
    - 1 for said helical scan, where P is a non-integer less than N.
  - 4. A method in accordance with claim 3 wherein N=4 and P=2.5.
  - 5. A method in accordance with claim 1 further comprising the step of applying a non-linear interpolation to the attenuation measurements prior to said filtering and backprojecting.
  - 6. A method in accordance with claim 5 wherein applying a non-linear interpolation to the attenuation measurements comprises applying a Lagrange interpolation to the attenuation measurements.
  - 7. A method in accordance with claim 6 wherein applying a Lagrange interpolation to the attenuation measurements comprises applying third order Lagrange interpolation weights to measurements from four detector rows.
  - 8. A method in accordance with claim 5 wherein the CT imaging system has 4 detector rows, helically scanning the object to obtain attenuation measurements comprises the step of helically scanning the object at a pitch of 2.5:
    - 1, and said estimating at least one projection along the curved plane of reconstruction comprises the step of estimating projections along the curved plane of reconstruction written as β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      , where β
      
      ₁′
      
      , β
      
      ₂′
      
      , β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles in a curved plane for corresponding detector rows R1, R2, R3, and R4, respectively, and γ
      
      represents a detector angle.
  - 9. A method in accordance with claim 5 wherein applying a non-linear interpolation to the attenuation measurements comprises combining weighted interpolated measurements with weighted extrapolated measurements.
  - 10. A method in accordance with claim 9 wherein the CT imaging system has 4 detector rows R1, R2, R3, and R4, helically scanning the object to obtain attenuation measurements comprises the step of helically scanning the object at a pitch of 2.5:
    - 1, and said method further comprises the step of applying weights to attenuation measurements for detector rows R1, R2, R3, and R4 respectively, wherein the applied weights are written as;
      
      $w_{1} (γ, β) = {\begin{matrix} [{(\frac{5 θ_{1} + 2 π}{2 π})}^{α} + {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{5 θ_{1} + 2 π}{2 π}), & β_{1}^{'} - \frac{2 π}{5} \leq β < β_{1}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{1} + 2 π}{2 π})}^{α} - {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{π - 5 θ_{1}}{π}) + \\ [{(\frac{5 θ_{1} + 2 π}{2 π})}^{α} + {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{5 θ_{1} + 2 π}{2 π}), \end{matrix} & β_{1}^{'} - \frac{π}{5} \leq β < β_{1}^{'} \\ [{(\frac{5 θ_{1}}{π})}^{α} + {(\frac{π - 5 θ_{1}}{π})}^{α}] (\frac{π - 5 θ_{1}}{π}), & β_{1}^{'} \leq β < β_{1}^{'} + \frac{π}{5} \end{matrix}$ where θ
      
      ₁=β
      
      −
      
      β
      
      ₁′
      
      =β
      
      −
      
      2.8π
      
      +γ
      
      , $w_{2} (γ, β) = {\begin{matrix} [1 - {(\frac{5 θ_{2} + 3 π}{2 π})}^{α} - {(\frac{- 5 θ_{2} - π}{2 π})}^{α}] (\frac{5 θ_{2} + π}{π}), & β_{2}^{'} - \frac{2 π}{5} \leq β < β_{2}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{2} + π}{π})}^{α} - {(\frac{- 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}) + \\ [{(\frac{5 θ_{2} + π}{π})}^{α} + {(\frac{- 5 θ_{2}}{2 π})}^{α}] (\frac{5 θ_{2} + π}{π}), \end{matrix} & β_{2}^{'} - \frac{π}{5} \leq β < β_{2}^{'} \\ [{(\frac{5 θ_{2}}{π})}^{α} + {(\frac{π - 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}), & β_{2}^{'} \leq β < β_{2}^{'} + \frac{π}{5} \\ [1 - {(\frac{5 θ_{2} - π}{π})}^{α} - {(\frac{2 π - 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}), & β_{2}^{'} + \frac{π}{5} \leq β < β_{2}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₂=β
      
      −
      
      β
      
      ₂′
      
      =β
      
      −
      
      2π
      
      +γ
      
      , $w_{3} (γ, β) = {\begin{matrix} \begin{matrix} [1 - {(\frac{5 θ_{3} + 2 π}{π})}^{α} - \\ {(\frac{- 5 θ_{3} - π}{π})}^{α}] (\frac{5 θ_{3} + π}{π}) \end{matrix} & β_{3}^{'} - \frac{2 π}{5} \leq β < β_{3}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{3} + π}{π})}^{α} - {(\frac{- 5 θ_{3}}{π})}^{α}] (\frac{π - 5 θ_{3}}{π}) + \\ [{(\frac{5 θ_{3} + π}{π})}^{α} + {(\frac{- 5 θ_{3}}{π})}^{α}] (\frac{5 θ_{3} + π}{π}) \end{matrix} & β_{3}^{'} - \frac{π}{5} \leq β < β_{3}^{'} \\ \begin{matrix} [1 - {(\frac{5 θ_{3}}{π})}^{α} - {(\frac{π - 5 θ_{3}}{π})}^{α}] (\frac{π + 5 θ_{3}}{π}) + \\ [{(\frac{5 θ_{3}}{π})}^{α} + {(\frac{π - 5 θ_{3}}{π})}^{α}] (\frac{π - 5 θ_{3}}{π}) \end{matrix} & β_{3}^{'} \leq β < β_{3}^{'} + \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{3} - π}{2 π})}^{α} - \\ {(\frac{3 π - 5 θ_{3}}{2 π})}^{α}] (\frac{π - 5 θ_{3}}{π}) \end{matrix} & β_{3}^{'} + \frac{π}{5} \leq β < β_{3}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₃=β
      
      −
      
      β
      
      ₃′
      
      =β
      
      −
      
      1.2π
      
      +γ
      
      , and $w_{4} (γ, β) = {\begin{matrix} \begin{matrix} [1 - {(\frac{5 θ_{4} + 2 π}{π})}^{α} - \\ {(\frac{- 5 θ_{4} - π}{π})}^{α}] (\frac{5 θ_{4} + π}{π}) \end{matrix} & β_{4}^{'} - \frac{2 π}{5} \leq β < β_{4}^{'} - \frac{π}{5} \\ [{(\frac{5 θ_{4} + π}{π})}^{α} + {(\frac{- 5 θ_{4}}{π})}^{α}] (\frac{π + 5 θ_{4}}{π}) & β_{4}^{'} - \frac{π}{5} \leq β < β_{4}^{'} \\ \begin{matrix} [1 - {(\frac{5 θ_{4}}{2 π})}^{α} - {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{π + 5 θ_{4}}{π}) + \\ [{(\frac{5 θ_{4}}{2 π})}^{α} + {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{2 π - 5 θ_{4}}{2 π}) \end{matrix} & β_{4}^{'} \leq β < β_{4}^{'} + \frac{π}{5} \\ \begin{matrix} [{(\frac{5 θ_{4}}{2 π})}^{α} + \\ {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{2 π - 5 θ_{4}}{2 π}) \end{matrix} & β_{4}^{'} + \frac{π}{5} \leq β < β_{4}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₄=β
      
      −
      
      β
      
      ₄′
      
      =β
      
      −
      
      0.4π
      
      +γ
      
      ,β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      ;
      
      β
      
      ₁′
      
      β
      
      ₂′
      
      β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles intersecting the POR for detector rows R1, R2, R3, and R4, respectively, andγ
      
      represents a detector angle.
  - 11. A method in accordance with claim 1 further comprising the step of applying a set of weights to the attenuation measurements prior to said filtering and backprojecting.
  - 12. A method in accordance with claim 11 wherein applying a set of weights to the attenuation measurements comprises the step of applying Lagrange weights to the attenuation measurements.
  - 13. A method in accordance with claim 12 wherein applying Lagrange weights to the attenuation measurements comprises applying third order Lagrange weights to measurements from four detector rows.
  - 14. A method in accordance with claim 11 wherein the CT imaging system has 4 detector rows, helically scanning the object to obtain attenuation measurements comprises the step of helically scanning the object at a pitch of 2.5:
    - 1, and said estimating at least one projection along the curved plane of reconstruction comprises the step of estimating projections along the curved plane of reconstruction written as β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      , where β
      
      ₁′
      
      , β
      
      ₂′
      
      , β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles in a curved plane for corresponding detector rows R1, R2, R3, and R4, respectively, and γ
      
      represents a detector angle.
  - 15. A method in accordance with claim 1 further comprising the step of applying interpolation and extrapolation to determine weights to be applied to the attenuation measurements.

16. A computed tomographic (CT) imaging system for imaging an object, said system comprising a radiation source and a multi-slice detector having a plurality of detector rows, said multi-slice detector configured to acquire attenuation measurements of an object between said radiation source and said multi-slice detector, said system configured to:
- helical scan the object to acquire attenuation measurements of the object, said measurements including more than two conjugate samples, wherein a difference between a view angle of one of the more than two conjugate samples and a view angle of any one of the remaining conjugate samples of the more than two conjugate samples is n π
  
  , wherein n is an integer greater than zero;
  
  estimate at least one projection along a curved plane of reconstruction of the object using the attenuation measurements of the object, including the more than two conjugate samples;
  
  applying different weighting functions within each detector row dependent upon a division of conjugate regions for each detector row and dependent upon view angles in a curved plane for corresponding detector rows; and
  
  filter and backproject the attenuation measurements of the object, including the more than two conjugate samples, to reconstruct at least one image slice of the object.
- View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
- - 17. A system in accordance with claim 16 further configured so that the more than two conjugate samples are located within a predetermined distance from the curved plane of reconstruction of the object.
  - 18. A system in accordance with claim 17 having N detector rows, and further configured to perform the helical scan at a pitch P:
    - 1, where P is a non-integer less than N.
  - 19. A system in accordance with claim 18 wherein N=4 and P=2.5.
  - 20. A system in accordance with claim 16 further configured to apply a non-linear interpolation to the attenuation measurements prior to said filtering and backprojecting.
  - 21. A system in accordance with claim 20 wherein said system being configured to apply a non-linear interpolation to the attenuation measurements comprises said system being configured to apply a Lagrange interpolation to the attenuation measurements.
  - 22. A system in accordance with claim 21 wherein said system being configured to apply a Lagrange interpolation to the attenuation measurements comprises said system being configured to apply third order Lagrange interpolation weights to measurements from four detector rows.
  - 23. A system in accordance with claim 20 having 4 detector rows, and wherein said system being configured to helically scan the object to obtain attenuation measurements comprises said system being configured to helically scan the object at a pitch of 2.5:
    - 1, and to estimate at least one projection along the curved plane of reconstruction said system is further configured to estimate projections along the curved plane of reconstruction written as β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      , where β
      
      ₁′
      
      , β
      
      ₂′
      
      , β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles in a curved plane for corresponding detector rows R1, R2, R3, and R4, respectively, and γ
      
      represents a detector angle.
  - 24. A system in accordance with claim 20 wherein said system being configured to apply a non-linear interpolation to the attenuation measurements comprises said system being configured to combine weighted interpolated measurements with weighted extrapolated measurements.
  - 25. A system in accordance with claim 24 having 4 detector rows R1, R2, R3, and R4, wherein said system being configured to helically scan the object to obtain attenuation measurements comprises said system being configured to helically scan the object at a pitch of 2.5:
    - 1, and said system is further configured to apply weights to attenuation measurements for detector rows R1, R2, R3, and R4 respectively, wherein the applied weights are written as;
      
      $w_{1} (γ, β) = {\begin{matrix} [{(\frac{5 θ_{1} + 2 π}{2 π})}^{α} + {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{5 θ_{1} + 2 π}{2 π}), & β_{1}^{'} - \frac{2 π}{5} \leq β < β_{1}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{1} + 2 π}{2 π})}^{α} - {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{π - 5 θ_{1}}{π}) + \\ [{(\frac{5 θ_{1} + 2 π}{2 π})}^{α} + {(\frac{- 5 θ_{1}}{2 π})}^{α}] (\frac{5 θ_{1} + 2 π}{2 π}), \end{matrix} & β_{1}^{'} - \frac{π}{5} \leq β < β_{1}^{'} \\ [{(\frac{5 θ_{1}}{π})}^{α} + {(\frac{π - 5 θ_{1}}{π})}^{α}] (\frac{π - 5 θ_{1}}{π}), & β_{1}^{'} \leq β < β_{1}^{'} + \frac{π}{5} \end{matrix}$ where θ
      
      ₁=β
      
      −
      
      β
      
      ₁′
      
      =β
      
      −
      
      2.8π
      
      +γ
      
      , $w_{2} (γ, β) = {\begin{matrix} [1 - {(\frac{5 θ_{2} + 3 π}{2 π})}^{α} - {(\frac{- 5 θ_{2} - π}{2 π})}^{α}] (\frac{5 θ_{2} + π}{π}), & β_{2}^{'} - \frac{2 π}{5} \leq β < β_{2}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{2} + π}{π})}^{α} - {(\frac{- 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}) + \\ [{(\frac{5 θ_{2} + π}{π})}^{α} + {(\frac{- 5 θ_{2}}{π})}^{α}] (\frac{5 θ_{2} + π}{π}), \end{matrix} & β_{2}^{'} - \frac{π}{5} \leq β < β_{2}^{'} \\ [{(\frac{5 θ_{2}}{π})}^{α} + {(\frac{π - 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}), & β_{2}^{'} \leq β < β_{2}^{'} + \frac{π}{5} \\ [1 - {(\frac{5 θ_{2} - π}{π})}^{α} - {(\frac{2 π - 5 θ_{2}}{π})}^{α}] (\frac{π - 5 θ_{2}}{π}), & β_{2}^{'} + \frac{π}{5} \leq β < β_{2}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₂=β
      
      −
      
      β
      
      ₂′
      
      =β
      
      −
      
      2π
      
      +γ
      
      , $w_{3} (γ, β) = {\begin{matrix} [1 - {(\frac{5 θ_{3} + 2 π}{π})}^{α} - {(\frac{- 5 θ_{3} - π}{π})}^{α}] (\frac{5 θ_{3} + π}{π}) & β_{3}^{'} - \frac{2 π}{5} \leq β < β_{3}^{'} - \frac{π}{5} \\ \begin{matrix} [1 - {(\frac{5 θ_{3} + π}{π})}^{α} - {(\frac{- 5 θ_{3}}{π})}^{α}] (\frac{π - 5 θ_{3}}{π}) + \\ [{(\frac{5 θ_{3} + π}{π})}^{α} + {(\frac{- 5 θ_{3}}{π})}^{α}] (\frac{5 θ_{3} + π}{π}) \end{matrix} & β_{3}^{'} - \frac{π}{5} \leq β < β_{3}^{'} \\ \begin{matrix} [1 - {(\frac{5 θ_{3}}{π})}^{α} - {(\frac{π - 5 θ_{3}}{π})}^{α}] (\frac{π + 5 θ_{3}}{π}) + \\ [{(\frac{5 θ_{3}}{π})}^{α} + {(\frac{π - 5 θ_{3}}{π})}^{α}] (\frac{π - 5 θ_{3}}{π}) \end{matrix} & β_{3}^{'} \leq β < β_{3}^{'} + \frac{π}{5} \\ [1 - {(\frac{5 θ_{3} - π}{2 π})}^{α} - {(\frac{3 π - 5 θ_{3}}{2 π})}^{α}] (\frac{π - 5 θ_{3}}{π}) & β_{3}^{'} + \frac{π}{5} \leq β < β_{3}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₃=β
      
      −
      
      β
      
      ₃′
      
      =β
      
      −
      
      1.2π
      
      +γ
      
      , and $w_{4} (γ, β) = {\begin{matrix} [1 - {(\frac{5 θ_{4} + 2 π}{π})}^{α} - {(\frac{- 5 θ_{4} - π}{π})}^{α}] (\frac{5 θ_{4} + π}{π}) & β_{4}^{'} - \frac{2 π}{5} \leq β < β_{4}^{'} - \frac{π}{5} \\ [{(\frac{5 θ_{4} + π}{π})}^{α} + {(\frac{- 5 θ_{4}}{π})}^{α}] (\frac{π + 5 θ_{4}}{π}) & β_{4}^{'} - \frac{π}{5} \leq β < β_{4}^{'} \\ \begin{matrix} [1 - {(\frac{5 θ_{4}}{2 π})}^{α} - {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{π + 5 θ_{4}}{π}) + \\ [{(\frac{5 θ_{4}}{2 π})}^{α} + {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{2 π - 5 θ_{4}}{2 π}) \end{matrix} & β_{4}^{'} \leq β < β_{4}^{'} + \frac{π}{5} \\ [{(\frac{5 θ_{4}}{2 π})}^{α} + {(\frac{2 π - 5 θ_{4}}{2 π})}^{α}] (\frac{2 π - 5 θ_{4}}{2 π}) & β_{4}^{'} + \frac{π}{5} \leq β < β_{4}^{'} + \frac{2 π}{5} \end{matrix}$ where θ
      
      ₄=β
      
      −
      
      β
      
      ₄′
      
      =β
      
      −
      
      0.4π
      
      +γ
      
      ,β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      ;
      
      β
      
      ₁′
      
      , β
      
      ₂′
      
      , β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles intersecting the POR for detector rows R1, R2, R3, and R4, respectively, andγ
      
      represents a detector angle.
  - 26. A system in accordance with claim 16 further configured to apply a set of weights to the attenuation measurements prior to said filtering and backprojecting.
  - 27. A system in accordance with claim 26 wherein said system being configured to apply a set of weights to the attenuation measurements comprises said system being configured to apply Lagrange weights to the attenuation measurements.
  - 28. A system in accordance with claim 27 wherein said system being configured to apply Lagrange weights to the attenuation measurements comprises said system being configured to apply third order Lagrange weights to measurements from four detector rows.
  - 29. A system in accordance with claim 16 having 4 detector rows, and said system being configured to helically scan the object to obtain attenuation measurements comprises said system being configured to helically scan the object at a pitch of 2.5:
    - 1, and to estimate at least one projection along the curved plane of reconstruction said system is further configured to estimate projections along the curved plane of reconstruction written as β
      
      ₁′
      
      =2.8π
      
      −
      
      γ
      
      , β
      
      ₂′
      
      =2π
      
      −
      
      γ
      
      , β
      
      ₃′
      
      =1.2π
      
      −
      
      γ
      
      , and β
      
      ₄′
      
      =0.4π
      
      −
      
      γ
      
      , where β
      
      ₁′
      
      , β
      
      ₂′
      
      , β
      
      ₃′
      
      , and β
      
      ₄′
      
      represent view angles in a curved plane for corresponding detector rows R1, R2, R3, and R4, respectively, and γ
      
      represents a detector angle.
  - 30. A system in accordance with claim 16 further configured to apply interpolation and extrapolation to determine weights to be applied to the attenuation measurements.

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Current Assignee
Nippon Mitsubishi Oil Corporation (ENEOS Holdings, Inc.), GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
Original Assignee
GE Medical Systems Global Technology Company LLC (GE Healthcare Technologies, Inc.)
Inventors
Hsieh, Jiang
Primary Examiner(s)
Ahmed, Samir
Assistant Examiner(s)
Kim, Charles

Application Number

US09/557,108
Time in Patent Office

2,073 Days
Field of Search

282/128, 282/131, 282/132, 378/4
US Class Current

382/131
CPC Class Codes

A61B 6/027   characterised by the use of...

A61B 6/032   Transmission computed tomog...

G01N 2223/419   computed tomograph

G01N 2223/612   biological material

G01N 23/046   using tomography, e.g. comp...

G06T 11/006   Inverse problem, transforma...

G06T 2211/421   Filtered back projection [FBP]

Methods and apparatus for helical reconstruction for multislice CT scan

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Methods and apparatus for helical reconstruction for multislice CT scan

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