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Interleaved acquisition for cross scatter avoidance in dual cone-beam CT.

Publication ,  Journal Article
Giles, W; Bowsher, J; Li, H; Yin, F-F
Published in: Med Phys
December 2012

PURPOSE: Cone-beam x-ray imaging with flat panel detectors is used for target localization in image guided radiation therapy. This imaging includes cone-beam computed tomography (CBCT) and planar imaging. Use of two orthogonal x-ray systems could reduce imaging time for CBCT, provide simultaneous orthogonal views in planar imaging, facilitate dual-energy methods, and be useful in alleviating cone-beam artifacts by providing two axially offset focal-spot trajectories. However, the potential advantages of a second cone-beam system come at the cost of cross scatter, i.e., scatter of photons originating from one tube into the noncorresponding detector. Herein, cross scatter is characterized for dual cone-beam imaging, and a method for avoiding cross scatter is proposed and evaluated. METHODS: A prototype dual-source CBCT system has been developed that models the geometry of a gantry-mounted kV imaging device used in radiation therapy. Cross scatter was characterized from 70 to 145 kVp in projections and reconstructed images using this system and three cylindrical phantoms (15, 20, and 30 cm) with a common Catphan core. A novel strategy for avoiding cross scatter in dual CBCT was developed that utilized interleaved data acquisition on each imaging chain. Interleaving, while maintaining similar angular sampling, can be achieved by either doubling the data acquisition rate or, as presented herein, halving the rotation speed. RESULTS: The ratio of cross scatter to the total detected signal was found to be as high as 0.59 in a 30 cm diameter phantom. The measured scatter-to-primary ratio in some cases exceeded 4. In the 30 cm phantom, reconstructed contrast was reduced across all ROIs by an average of 48.7% when cross scatter was present. These cross-scatter degradations were almost entirely avoided by the method of interleaved exposures. CONCLUSIONS: Cross scatter is substantial in dual cone-beam imaging, but its effects can be largely removed by interleaved acquisition, which can be achieved at the same angular sampling rate either by doubling the data acquisition rate or halving the rotation speed.

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Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

December 2012

Volume

39

Issue

12

Start / End Page

7719 / 7728

Location

United States

Related Subject Headings

  • Sensitivity and Specificity
  • Reproducibility of Results
  • Radiographic Image Interpretation, Computer-Assisted
  • Radiographic Image Enhancement
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Cone-Beam Computed Tomography
  • Artifacts
  • Algorithms
  • 5105 Medical and biological physics
 

Citation

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Giles, W., Bowsher, J., Li, H., & Yin, F.-F. (2012). Interleaved acquisition for cross scatter avoidance in dual cone-beam CT. Med Phys, 39(12), 7719–7728. https://doi.org/10.1118/1.4768160
Giles, William, James Bowsher, Hao Li, and Fang-Fang Yin. “Interleaved acquisition for cross scatter avoidance in dual cone-beam CT.Med Phys 39, no. 12 (December 2012): 7719–28. https://doi.org/10.1118/1.4768160.
Giles W, Bowsher J, Li H, Yin F-F. Interleaved acquisition for cross scatter avoidance in dual cone-beam CT. Med Phys. 2012 Dec;39(12):7719–28.
Giles, William, et al. “Interleaved acquisition for cross scatter avoidance in dual cone-beam CT.Med Phys, vol. 39, no. 12, Dec. 2012, pp. 7719–28. Pubmed, doi:10.1118/1.4768160.
Giles W, Bowsher J, Li H, Yin F-F. Interleaved acquisition for cross scatter avoidance in dual cone-beam CT. Med Phys. 2012 Dec;39(12):7719–7728.

Published In

Med Phys

DOI

ISSN

0094-2405

Publication Date

December 2012

Volume

39

Issue

12

Start / End Page

7719 / 7728

Location

United States

Related Subject Headings

  • Sensitivity and Specificity
  • Reproducibility of Results
  • Radiographic Image Interpretation, Computer-Assisted
  • Radiographic Image Enhancement
  • Phantoms, Imaging
  • Nuclear Medicine & Medical Imaging
  • Cone-Beam Computed Tomography
  • Artifacts
  • Algorithms
  • 5105 Medical and biological physics