Reduction in x-ray scatter and radiation dose for volume-of-interest (VOI) cone-beam breast CT - A phantom study

Chao Jen Lai, Lingyun Chen, Huojun Zhang, Xinming Liu, Yuncheng Zhong, Youtao Shen, Tao Han, Shuaiping Ge, Ying Yi, Tianpeng Wang, Wei T. Yang, Gary J. Whitman, Chris C. Shaw

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

With volume-of-interest (VOI) cone-beam computed tomography (CBCT) imaging, one set of projection images are acquired with the VOI collimator at a regular or high exposure level and the second set of projection images are acquired without the collimator at a reduced exposure level. The high exposure VOI scan data inside the VOI and the low exposure full-field scan data outside the VOI are then combined together to generate composite projection images for image reconstruction. To investigate and quantify scatter reduction, dose saving and image quality improvement in VOI CBCT imaging, a flat panel detector-based bench-top experimental CBCT system was built to measure the dose, the scatter-to-primary ratio (SPR), the image contrast, noise level, the contrast-to-noise ratio (CNR) and the figure of merit (FOM) in the CBCT reconstructed images for two polycarbonate cylinders simulating the small and the large phantoms. The results showed that, compared to the full field CBCT technique, radiation doses for the VOI CBCT technique were reduced by a factor of 1.20 and 1.36 for the small and the large phantoms at the phantom center, respectively, and from 2.7 to 3.0 on the edge of the phantom, respectively. Inside the VOI, the SPRs were substantially reduced by a factor of 6.6 and 10.3 for the small and the large phantoms, the contrast signals were improved by a factor of 1.35 and 1.8, and the noise levels were increased by a factor of 1.27 and 1.6, respectively. As a result, the CNRs were improved by a factor of 1.06 and 1.13 for the small and the large phantoms and the FOM improved by a factor of 1.4 and 1.7, respectively.

Original languageEnglish (US)
Pages (from-to)6691-6709
Number of pages19
JournalPhysics in medicine and biology
Volume54
Issue number21
DOIs
StatePublished - Nov 16 2009

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

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    Lai, C. J., Chen, L., Zhang, H., Liu, X., Zhong, Y., Shen, Y., Han, T., Ge, S., Yi, Y., Wang, T., Yang, W. T., Whitman, G. J., & Shaw, C. C. (2009). Reduction in x-ray scatter and radiation dose for volume-of-interest (VOI) cone-beam breast CT - A phantom study. Physics in medicine and biology, 54(21), 6691-6709. https://doi.org/10.1088/0031-9155/54/21/016