Multi-sector back-off logic algorithm for obtaining optimal slice-sensitive computed tomography profiles

Abstract

A multi-sector back-off logic algorithm for obtaining optimal slice-sensitive computed tomography (“CT”) profiles. The systems and methods of the present invention improving the temporal resolution of a CT system by checking for Z location errors between sectors and automatically backing-off to an alternative multi-sector algorithm when necessary (i.e., selecting an optimized maximum number of sectors to reconstruct), providing less Z location error. Based upon this Z location error, the systems and methods of the present invention also calculating the maximum number of sectors that should be used for reconstruction “on-the-fly” (i.e., on a per image basis across an entire series of images). These systems and methods utilizing the Recommended Protocol for Cardiac Reconstruction Algorithms.

1. A computed tomography method, comprising:
 determining a maximum Z location error;  
 determining a weighted average Z location error;  
 selecting a threshold value associated with the maximum Z location error and the weighted average Z location error;  
 prescribing an N+1 sector reconstruction algorithm;  
 if the maximum Z location error is less than the threshold value or the weighted average Z location error is less than the threshold value, performing an N+1 sector reconstruction; and  
 if the maximum Z location error exceeds the threshold value or the weighted average Z location error exceeds the threshold value, prescribing an N sector reconstruction.  
 
     
     
       2. The computed tomography method of  claim 1 , further comprising, if the  a second maximum Z location error is less than the threshold value or the  a second weighted average Z location error is less than the threshold value, performing an N sector reconstruction. 
     
     
       3. The computed tomography method of  claim 2 , further comprising, if the second maximum Z location error exceeds the threshold value or the second weighted average Z location error exceeds the threshold value, prescribing an N−1 sector reconstruction. 
     
     
       4. The computed tomography method of  claim 1 , wherein the computed tomography method is used to perform cardiac imaging. 
     
     
       5. A computed tomography method for obtaining optimal slice-sensitive profiles, comprising:
 determining a maximum Z location error associated with a computed tomography system;  
 determining a weighted average Z location error associated with the computed tomography system;  
 selecting a threshold value associated with the maximum Z location error and the weighted average Z location error;  
 prescribing an N+1 sector reconstruction algorithm;  
 if the maximum Z location error is less than the threshold value or the weighted average Z location error is less than the threshold value, performing an N+1 sector reconstruction; and  
 if the maximum Z location error exceeds the threshold value or the weighted average Z location error exceeds the threshold value, prescribing an N sector reconstruction.  
 
     
     
       6. The computed tomography method of  claim 5 , further comprising, if the  a second maximum Z location error is less than the threshold value or the  a second weighted average Z location error is less than the threshold value, performing an N sector reconstruction. 
     
     
       7. The computed tomography method of  claim 6 , further comprising, if the second maximum Z location error exceeds the threshold value or the second weighted average Z location error exceeds the threshold value, prescribing an N−1 sector reconstruction. 
     
     
       8. The computed tomography method of  claim 5 , wherein the computed tomography method is used to perform cardiac imaging. 
     
     
       9. An imaging method for obtaining optimal slice-sensitive profiles, comprising:
 determining a maximum Z location error associated with an imaging system;  
 determining a weighted average Z location error associated with the imaging system;  
 selecting a threshold value associated with the maximum Z location error and the weighted average Z location error;  
 prescribing an N+1 sector reconstruction algorithm;  
 if the maximum Z location error is less than the threshold value or the weighted average Z location error is less than the threshold value, performing an N+1 sector reconstruction; and  
 if the maximum Z location error exceeds the threshold value or the weighted average Z location error exceeds the threshold value, prescribing an N sector reconstruction.  
 
     
     
       10. The imaging method of  claim 9 , further comprising, if the  a second maximum Z location error is less than the threshold value or the  a second weighted average Z location error is less than the threshold value, performing an N sector reconstruction. 
     
     
       11. The imaging method of  claim 10 , further comprising, if the second maximum Z location error exceeds the threshold value or the second weighted average Z location error exceeds the threshold value, prescribing an N−1 sector reconstruction. 
     
     
       12. The imaging method of  claim 9 , wherein the computed tomography  imaging method is used to perform cardiac imaging. 
     
     
       13. A computed tomography system, comprising:
 a computed tomography scanner;  
 a first algorithm operable for determining a maximum Z location error associated with the computed tomography system;  
 a second algorithm operable for determining a weighted average Z location error associated with the computed tomography system;  
 a third algorithm operable for selecting a threshold value associated with the maximum Z location error and the weighted average Z location error;  
 means for prescribing an N+1 sector reconstruction algorithm;  
 a fourth algorithm operable for, if the maximum Z location error is less than the threshold value or the weighted average Z location error is less than the threshold value, performing an N+1 sector reconstruction; and  
 wherein the fourth algorithm is further operable for, if the maximum Z location error exceeds the threshold value or the weighted average Z location error exceeds the threshold value, prescribing an N sector reconstruction.  
 
     
     
       14. The computed tomography system of  claim 13 , wherein the fourth algorithm is further operable for, if the  a second maximum Z location error is less than the threshold value or the  a second weighted average Z location error is less than the threshold value, performing an N sector reconstruction. 
     
     
       15. The computed tomography system of  claim 14 , wherein the fourth algorithm is further operable for, if the second maximum Z location error exceeds the threshold value or the second weighted average Z location error exceeds the threshold value, prescribing an N−1 sector reconstruction. 
     
     
       16. The computed tomography system of  claim 13 , wherein the computed tomography system is used to perform cardiac imaging. 
     
     
       17. An imaging system, comprising:
 an imaging scanner;  
 a first algorithm operable for determining a maximum Z location error associated with the imaging system;  
 a second algorithm operable for determining a weighted average Z location error associated with the imaging system;  
 a third algorithm operable for selecting a threshold value associated with the maximum Z location error and the weighted average Z location error;  
 means for prescribing an N+1 sector reconstruction algorithm;  
 a fourth algorithm operable for, if the maximum Z location error is less than the threshold value or the weighted average Z location error is less than the threshold value, performing an N+1 sector reconstruction; and  
 wherein the fourth algorithm is further operable for, if the maximum Z location error exceeds the threshold value or the weighted average Z location error exceeds the threshold value, prescribing an N sector reconstruction.  
 
     
     
       18. The imaging system of  claim 17 , wherein the fourth algorithm is further operable for, if the  a second maximum Z location error is less than the threshold value or the  a second weighted average Z location error is less than the threshold value, performing an N sector reconstruction. 
     
     
       19. The imaging system of  claim 18 , wherein the fourth algorithm is further operable for, if the second maximum Z location error exceeds the threshold value or the second weighted average Z location error exceeds the threshold value, prescribing an N−1 sector reconstruction. 
     
     
       20. The imaging system of  claim 17 , wherein the imaging system is used to perform cardiac imaging. 
     
     
       21. The computed tomography method of  claim 1  wherein:
   determining the maximum Z location error further comprises determining a first maximum Z location error and a second maximum Z location error; and        determining the weighted average Z location error further comprises determining a first weighted average Z location error and a second weighted average Z location error.     
     
     
       22. The computed tomography method of  claim 5  wherein:
   determining the maximum Z location error further comprises determining a first maximum Z location error and a second maximum Z location error; and        determining the weighted average Z location error further comprises determining a first weighted average Z location error and a second weighted average Z location error.     
     
     
       23. The imaging method of  claim 9  wherein:
   determining the maximum Z location error further comprises determining a first maximum Z location error and a second maximum Z location error; and        determining the weighted average Z location error further comprises determining a first weighted average Z location error and a second weighted average Z location error.     
     
     
       24. The computed tomography system of  claim 13  wherein:
   the first algorithm is further operable for determining a first maximum Z location error and a second maximum Z location error; and        the second algorithm is further operable for determining a first weighted average Z location error and a second weighted average Z location error.     
     
     
       25. The imaging system of  claim 17  wherein:
   the first algorithm is further operable for determining a first maximum Z location error and a second maximum Z location error; and        the second algorithm is further operable for determining a first weighted average Z location error and a second weighted average Z location error.     
     
     
       26. An imaging apparatus comprising:
   an imager; and        a computer programmed to:      acquire scan data;        select a predetermined number of sectors corresponding to the scan data;        determine a multiple - sector Z location error corresponding to the predetermined number of sectors for a desired Z location;        select a Z location error threshold;        reconstruct an image from less than the predetermined number of sectors if the multiple - sector Z location error is above the Z location error threshold; otherwise        reconstruct an image from the predetermined number of sectors.       
     
     
       27. The imaging apparatus of  claim 26  wherein the computer is further programmed to:
   determine a Z location for each of the predetermined number of sectors;        determine a detector coverage associated with the imager;        calculate an upper limit and a lower limit of the detector coverage for each of the predetermined number of sectors; and        determine a single - sector Z location error for each of the predetermined number of sectors based on the respective Z location, the upper limit, and the lower limit of each sector.     
     
     
       28. The imaging apparatus of  claim 27  wherein the computer is further programmed to:
   set the single - sector Z location error for each sector equal to the lower limit minus the Z location, if the respective single - sector Z location is less than the lower limit;        set the single - sector Z location error for each sector equal to the upper limit minus the Z location, if the respective single - sector Z location is greater than the upper limit; otherwise        set the single - sector Z location equal to zero.     
     
     
       29. The imaging apparatus of  claim 27  wherein the computer is further programmed to:
   identify an upper - most Z location error sector of the predetermined number of sectors based on the single - sector Z location error of each sector;        identify a lower - most Z location error sector from the predetermined number of sectors based on the single - sector Z location error of each sector; and        determine the multi - sector Z location error by calculating a maximum Z location error based on the upper - most Z location error sector and the lower - most Z location error sector.     
     
     
       30. The imaging apparatus of  claim 29  wherein the computer is further programmed to calculate the maximum Z location error in accordance with:
   maximum   —   error   —   spread=maximum   —   error−minimum   —   error        where:        maximum   —   error represents the single - sector Z location error corresponding to the upper - most Z location error sector and minimum   —   error represents the single - sector Z location error corresponding to the lower - most Z location error sector.     
     
     
       31. The imaging apparatus of  claim 29  wherein the computer is further programmed to determine the multiple- sector Z location error by calculating a weighted average Z location error based on the upper - most Z location error sector and the lower - most Z location error sector.   
     
     
       32. The imaging apparatus of  claim 31  wherein the computer is further programmed to calculate the weighted average Z location error in accordance with:
   WE=total error over all sectors/total view over all sectors        where:        WE represents the weighted average Z location error and total error over all sectors represents a total Z location error over all sectors.     
     
     
       33. An imaging method comprising:
   accessing a predetermined number of sectors to reconstruct;        receiving scan data associated with the predetermined number of sectors;        determining a Z location error threshold;        determining a plurality of Z locations for a desired Z location corresponding to the predetermined number of sectors;        calculating a first multi - sector Z location error based on the plurality of Z locations;        reconstructing less than the predetermined number of sectors to create an image if the first multi - sector Z location error is above the Z location error threshold; otherwise        reconstructing the predetermined number of sectors to create an image.     
     
     
       34. The method of  claim 33  further comprising:
   determining a plurality of detector coverage limits, each detector coverage limit corresponding to a respective one of the predetermined number of sectors;        determining a plurality of single - sector Z location errors based on the plurality of detector coverage limits; and        calculating the first multi - sector Z location error based on the plurality of single - sector Z location errors.     
     
     
       35. The method of  claim 33  wherein reconstructing less than the predetermined number of sectors further comprises:
   calculating a second multi - sector Z location error based on the plurality of Z locations; and        reconstructing a set of sectors having one less sector than the predetermined number of sectors if the second multi - sector Z location error is below the Z location error threshold.     
     
     
       36. The method of  claim 33  wherein calculating the first multi- sector Z location error comprises calculating a maximum Z location error and a weighted average Z location error based on the plurality of Z locations.   
     
     
       37. The method of  claim 33  wherein calculating the maximum Z location error comprises determining a maximum error between an upper most sector and a lower most sector of the predetermined number of sectors. 
     
     
       38. The method of  claim 36  wherein calculating the weighted average Z location error comprises determining an average Z location error weighted by a total view of the predetermined number of sectors.