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A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup

Publication ,  Journal Article
Guan, H; Hammoud, R; Yin, FF
Published in: Journal of Applied Clinical Medical Physics
January 1, 2009

A positioning QA procedure for Varian's 2D/2D (kV/MV) and 3D/3D (planCT/CBCT) matching was developed. The procedure was to check: (1) the coincidence of on-board imager (OBI), portal imager (PI), and cone beam CT (CBCT)'s isocenters (digital graticules) to a linac's isocenter (to a pre-specified accuracy); (2) that the positioning difference detected by 2D/2D (kV/MV) and 3D/3D(planCT/CBCT) matching can be reliably transferred to couch motion. A cube phantom with a 2 mm metal ball (bb) at the center was used. The bb was used to define the isocenter. Two additional bbs were placed on two phantom surfaces in order to define a spatial location of 1.5 cm anterior, 1.5 cm inferior, and 1.5 cm right from the isocenter. An axial scan of the phantom was acquired from a multislice CT simulator. The phantom was set at the linac's isocenter (lasers); either AP MV/R Lat kV images or CBCT images were taken for 2D/2D or 3D/3D matching, respectively. For 2D/2D, the accuracy of each device's isocenter was obtained by checking the distance between the central bb and the digital graticule. Then the central bb in orthogonal DRRs was manually moved to overlay to the off-axis bbs in kV/MV images. For 3D/3D, CBCT was first matched to planCT to check the isocenter difference between the two CTs. Manual shifts were then made by moving CBCT such that the point defined by the two off-axis bbs overlay to the central bb in planCT. (PlanCT can not be moved in the current version of OBI1.4.) The manual shifts were then applied to remotely move the couch. The room laser was used to check the accuracy of the couch movement. For Trilogy (or Ix-21) linacs, the coincidence of imager and linac's isocenter was better than 1 mm (or 1.5 mm). The couch shift accuracy was better than 2 mm.

Duke Scholars

Published In

Journal of Applied Clinical Medical Physics

DOI

EISSN

1526-9914

Publication Date

January 1, 2009

Volume

10

Issue

4

Start / End Page

273 / 280

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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ICMJE
MLA
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Guan, H., Hammoud, R., & Yin, F. F. (2009). A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup. Journal of Applied Clinical Medical Physics, 10(4), 273–280. https://doi.org/10.1120/jacmp.v10i4.2954
Guan, H., R. Hammoud, and F. F. Yin. “A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup.” Journal of Applied Clinical Medical Physics 10, no. 4 (January 1, 2009): 273–80. https://doi.org/10.1120/jacmp.v10i4.2954.
Guan H, Hammoud R, Yin FF. A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup. Journal of Applied Clinical Medical Physics. 2009 Jan 1;10(4):273–80.
Guan, H., et al. “A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup.” Journal of Applied Clinical Medical Physics, vol. 10, no. 4, Jan. 2009, pp. 273–80. Scopus, doi:10.1120/jacmp.v10i4.2954.
Guan H, Hammoud R, Yin FF. A positioning QA procedure for 2D/2D (kV/MV) and 3D/3D (CT/CBCT) image matching for radiotherapy patient setup. Journal of Applied Clinical Medical Physics. 2009 Jan 1;10(4):273–280.

Published In

Journal of Applied Clinical Medical Physics

DOI

EISSN

1526-9914

Publication Date

January 1, 2009

Volume

10

Issue

4

Start / End Page

273 / 280

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