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Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system

Publication ,  Journal Article
Kim, S; Song, H; Samei, E; Yin, FF; Yoshizumi, TT
Published in: Journal of Applied Clinical Medical Physics
January 1, 2011

Dosimetry in kilovoltage cone beam computed tomography (CBCT) is a challenge due to the limitation of physical measurements. To address this, we used a Monte Carlo (MC) method to estimate the CT dose index (CTDI) and the dose length product (DLP) for a commercial CBCT system. As Dixon and Boone(1) showed that CTDI concept can be applicable to both CBCT and conventional CT, we evaluated weighted CT dose index (CTDIw) and DLP for a commercial CBCT system. Two extended CT phantoms were created in our BEAMnrc/EGSnrc MC system. Before the simulations, the beam collimation of a Varian On-Board Imager (OBI) system was measured with radiochromic films (model: XR-QA). The MC model of the OBI X-ray tube, validated in a previous study, was used to acquire the phase space files of the full-fan and half-fan cone beams. Then, DOSXYZnrc user code simulated a total of 20 CBCT scans for the nominal beam widths from 1 cm to 10 cm. After the simulations, CBCT dose profiles at center and peripheral locations were extracted and integrated (dose profile integral, DPI) to calculate the CTDI per each beam width. The weighted cone-beam CTDI (CTDIw,l) was calculated from DPI values and mean CTDIw,l (CTDIw,l) and DLP were derived. We also evaluated the differences of CTDIw,1 values between MC simulations and point dose measurements using standard CT phantoms. In results, it was found that,CTDI600w was 8.74 ± 0.01 cGy for head and CTDI900w was 4.26 ± 0.01 cGy for body scan. The DLP was found to be proportional to the beam collimation. We also found that the point dose measurements with standard CT phantoms can estimate the CTDI within 3% difference compared to the full integrated CTDI from the MC method. This study showed the usability of CTDI as a dose index and DLP as a total dose descriptor in CBCT scans.

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Published In

Journal of Applied Clinical Medical Physics

DOI

EISSN

1526-9914

Publication Date

January 1, 2011

Volume

12

Issue

2

Start / End Page

84 / 95

Related Subject Headings

  • Nuclear Medicine & Medical Imaging
  • 5105 Medical and biological physics
  • 3208 Medical physiology
  • 1116 Medical Physiology
  • 1103 Clinical Sciences
  • 0299 Other Physical Sciences
 

Citation

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Chicago
ICMJE
MLA
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Kim, S., Song, H., Samei, E., Yin, F. F., & Yoshizumi, T. T. (2011). Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system. Journal of Applied Clinical Medical Physics, 12(2), 84–95. https://doi.org/10.1120/jacmp.v12i2.3395
Kim, S., H. Song, E. Samei, F. F. Yin, and T. T. Yoshizumi. “Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system.” Journal of Applied Clinical Medical Physics 12, no. 2 (January 1, 2011): 84–95. https://doi.org/10.1120/jacmp.v12i2.3395.
Kim S, Song H, Samei E, Yin FF, Yoshizumi TT. Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system. Journal of Applied Clinical Medical Physics. 2011 Jan 1;12(2):84–95.
Kim, S., et al. “Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system.” Journal of Applied Clinical Medical Physics, vol. 12, no. 2, Jan. 2011, pp. 84–95. Scopus, doi:10.1120/jacmp.v12i2.3395.
Kim S, Song H, Samei E, Yin FF, Yoshizumi TT. Computed tomography dose index and dose length product for cone-beam CT: Monte Carlo simulations of a commercial system. Journal of Applied Clinical Medical Physics. 2011 Jan 1;12(2):84–95.

Published In

Journal of Applied Clinical Medical Physics

DOI

EISSN

1526-9914

Publication Date

January 1, 2011

Volume

12

Issue

2

Start / End Page

84 / 95

Related Subject Headings

  • Nuclear Medicine & Medical Imaging
  • 5105 Medical and biological physics
  • 3208 Medical physiology
  • 1116 Medical Physiology
  • 1103 Clinical Sciences
  • 0299 Other Physical Sciences