Accuracy evaluation of a six-degree-of-freedom couch using cone beam CT and IsoCal phantom with an in-house algorithm

Qinghui Zhang, Joseph Driewer, Shuo Wang, Sicong Li, Xiaofeng Zhu, Dandan Zheng, Yijian Cao, Jiaju Zhang, Abolghassem Jamshidi, Brett W. Cox, Jonathan P.S. Knisely, Louis Potters, Eric E. Klein

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Purpose: The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. Methods: Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees were tested in one degree increments. A total of 49 combinations were tested at 0 degrees of yaw (couch rotation angle). The 3D positions of 16 tungsten carbide ball bearings (BBs), each 4 mm in diameter and arranged in a known geometry within the IsoCal phantom, were determined in the 49 image sets with in-house software. The BB positions at different rotation angles were determined using a rotation matrix from the original BB positions at zero pitch and roll angles. A linear least squares fit method estimated the rotation angles and differences between detected and nominal rotation angles were calculated. This study was conducted for the case with and without extra weight on the couch. Couch walk shifts for the system were investigated using eight combinations of rotation, roll and pitch. Results: A total of 49 CBCT images with voxel sizes 0.5 × 0.5 × 1.0 mm3 were taken for the case without extra weight on the couch. The 16 BBs were determined to evaluate the isocenter translation and rotation differences between the calculated and nominal couch values. Among all 49 calculations, the maximum rotation angle differences were 0.10 degrees for pitch, 0.15 degrees for roll and 0.09 degrees for yaw. The corresponding mean and standard deviation values were 0.028 ± 0.032, -0.043 ± 0.058, and -0.009 ± 0.033 degrees. The maximum translation differences were 0.3 mm in the left-right direction, 0.5 mm in the anterior-posterior direction and 0.4 mm in the superior-inferior direction. The mean values and corresponding standard deviations were 0.07 ± 0.12, -0.05 ± 0.25, and -0.12±0.14 mm for the planes described above. With an 80 kg phantom on the couch, the maximum translation shift was 0.69 mm. The couch walk translation shifts were less than 0.1 mm and rotation shifts were less than 0.1 degree. Conclusions: Errors of a new 6DoF couch were tested using CBCT images of a 3D phantom. The rotation errors were less than 0.3 degree and the translation errors were less than or equal to 0.8 mm in each direction. This level of accuracy is warranted for clinical radiotherapy utilization including stereotactic radiosurgery.

Original languageEnglish (US)
Pages (from-to)3888-3898
Number of pages11
JournalMedical Physics
Volume44
Issue number8
DOIs
StatePublished - Aug 1 2017

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Yaws
Cone-Beam Computed Tomography
Weights and Measures
Radiosurgery
Least-Squares Analysis
Radiotherapy
Software
Direction compound
tungsten carbide

Keywords

  • isocenter calibration
  • rotation
  • six degree couch

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

Cite this

Accuracy evaluation of a six-degree-of-freedom couch using cone beam CT and IsoCal phantom with an in-house algorithm. / Zhang, Qinghui; Driewer, Joseph; Wang, Shuo; Li, Sicong; Zhu, Xiaofeng; Zheng, Dandan; Cao, Yijian; Zhang, Jiaju; Jamshidi, Abolghassem; Cox, Brett W.; Knisely, Jonathan P.S.; Potters, Louis; Klein, Eric E.

In: Medical Physics, Vol. 44, No. 8, 01.08.2017, p. 3888-3898.

Research output: Contribution to journalArticle

Zhang, Q, Driewer, J, Wang, S, Li, S, Zhu, X, Zheng, D, Cao, Y, Zhang, J, Jamshidi, A, Cox, BW, Knisely, JPS, Potters, L & Klein, EE 2017, 'Accuracy evaluation of a six-degree-of-freedom couch using cone beam CT and IsoCal phantom with an in-house algorithm', Medical Physics, vol. 44, no. 8, pp. 3888-3898. https://doi.org/10.1002/mp.12342
Zhang, Qinghui ; Driewer, Joseph ; Wang, Shuo ; Li, Sicong ; Zhu, Xiaofeng ; Zheng, Dandan ; Cao, Yijian ; Zhang, Jiaju ; Jamshidi, Abolghassem ; Cox, Brett W. ; Knisely, Jonathan P.S. ; Potters, Louis ; Klein, Eric E. / Accuracy evaluation of a six-degree-of-freedom couch using cone beam CT and IsoCal phantom with an in-house algorithm. In: Medical Physics. 2017 ; Vol. 44, No. 8. pp. 3888-3898.
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abstract = "Purpose: The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. Methods: Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees were tested in one degree increments. A total of 49 combinations were tested at 0 degrees of yaw (couch rotation angle). The 3D positions of 16 tungsten carbide ball bearings (BBs), each 4 mm in diameter and arranged in a known geometry within the IsoCal phantom, were determined in the 49 image sets with in-house software. The BB positions at different rotation angles were determined using a rotation matrix from the original BB positions at zero pitch and roll angles. A linear least squares fit method estimated the rotation angles and differences between detected and nominal rotation angles were calculated. This study was conducted for the case with and without extra weight on the couch. Couch walk shifts for the system were investigated using eight combinations of rotation, roll and pitch. Results: A total of 49 CBCT images with voxel sizes 0.5 × 0.5 × 1.0 mm3 were taken for the case without extra weight on the couch. The 16 BBs were determined to evaluate the isocenter translation and rotation differences between the calculated and nominal couch values. Among all 49 calculations, the maximum rotation angle differences were 0.10 degrees for pitch, 0.15 degrees for roll and 0.09 degrees for yaw. The corresponding mean and standard deviation values were 0.028 ± 0.032, -0.043 ± 0.058, and -0.009 ± 0.033 degrees. The maximum translation differences were 0.3 mm in the left-right direction, 0.5 mm in the anterior-posterior direction and 0.4 mm in the superior-inferior direction. The mean values and corresponding standard deviations were 0.07 ± 0.12, -0.05 ± 0.25, and -0.12±0.14 mm for the planes described above. With an 80 kg phantom on the couch, the maximum translation shift was 0.69 mm. The couch walk translation shifts were less than 0.1 mm and rotation shifts were less than 0.1 degree. Conclusions: Errors of a new 6DoF couch were tested using CBCT images of a 3D phantom. The rotation errors were less than 0.3 degree and the translation errors were less than or equal to 0.8 mm in each direction. This level of accuracy is warranted for clinical radiotherapy utilization including stereotactic radiosurgery.",
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T1 - Accuracy evaluation of a six-degree-of-freedom couch using cone beam CT and IsoCal phantom with an in-house algorithm

AU - Zhang, Qinghui

AU - Driewer, Joseph

AU - Wang, Shuo

AU - Li, Sicong

AU - Zhu, Xiaofeng

AU - Zheng, Dandan

AU - Cao, Yijian

AU - Zhang, Jiaju

AU - Jamshidi, Abolghassem

AU - Cox, Brett W.

AU - Knisely, Jonathan P.S.

AU - Potters, Louis

AU - Klein, Eric E.

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N2 - Purpose: The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. Methods: Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees were tested in one degree increments. A total of 49 combinations were tested at 0 degrees of yaw (couch rotation angle). The 3D positions of 16 tungsten carbide ball bearings (BBs), each 4 mm in diameter and arranged in a known geometry within the IsoCal phantom, were determined in the 49 image sets with in-house software. The BB positions at different rotation angles were determined using a rotation matrix from the original BB positions at zero pitch and roll angles. A linear least squares fit method estimated the rotation angles and differences between detected and nominal rotation angles were calculated. This study was conducted for the case with and without extra weight on the couch. Couch walk shifts for the system were investigated using eight combinations of rotation, roll and pitch. Results: A total of 49 CBCT images with voxel sizes 0.5 × 0.5 × 1.0 mm3 were taken for the case without extra weight on the couch. The 16 BBs were determined to evaluate the isocenter translation and rotation differences between the calculated and nominal couch values. Among all 49 calculations, the maximum rotation angle differences were 0.10 degrees for pitch, 0.15 degrees for roll and 0.09 degrees for yaw. The corresponding mean and standard deviation values were 0.028 ± 0.032, -0.043 ± 0.058, and -0.009 ± 0.033 degrees. The maximum translation differences were 0.3 mm in the left-right direction, 0.5 mm in the anterior-posterior direction and 0.4 mm in the superior-inferior direction. The mean values and corresponding standard deviations were 0.07 ± 0.12, -0.05 ± 0.25, and -0.12±0.14 mm for the planes described above. With an 80 kg phantom on the couch, the maximum translation shift was 0.69 mm. The couch walk translation shifts were less than 0.1 mm and rotation shifts were less than 0.1 degree. Conclusions: Errors of a new 6DoF couch were tested using CBCT images of a 3D phantom. The rotation errors were less than 0.3 degree and the translation errors were less than or equal to 0.8 mm in each direction. This level of accuracy is warranted for clinical radiotherapy utilization including stereotactic radiosurgery.

AB - Purpose: The accuracy of a six degree of freedom (6DoF) couch was evaluated using a novel method. Methods: Cone beam CT (CBCT) images of a 3D phantom (IsoCal) were acquired with different, known combinations of couch pitch and roll angles. Pitch and roll angles between the maximum allowable values of 357 and 3 degrees were tested in one degree increments. A total of 49 combinations were tested at 0 degrees of yaw (couch rotation angle). The 3D positions of 16 tungsten carbide ball bearings (BBs), each 4 mm in diameter and arranged in a known geometry within the IsoCal phantom, were determined in the 49 image sets with in-house software. The BB positions at different rotation angles were determined using a rotation matrix from the original BB positions at zero pitch and roll angles. A linear least squares fit method estimated the rotation angles and differences between detected and nominal rotation angles were calculated. This study was conducted for the case with and without extra weight on the couch. Couch walk shifts for the system were investigated using eight combinations of rotation, roll and pitch. Results: A total of 49 CBCT images with voxel sizes 0.5 × 0.5 × 1.0 mm3 were taken for the case without extra weight on the couch. The 16 BBs were determined to evaluate the isocenter translation and rotation differences between the calculated and nominal couch values. Among all 49 calculations, the maximum rotation angle differences were 0.10 degrees for pitch, 0.15 degrees for roll and 0.09 degrees for yaw. The corresponding mean and standard deviation values were 0.028 ± 0.032, -0.043 ± 0.058, and -0.009 ± 0.033 degrees. The maximum translation differences were 0.3 mm in the left-right direction, 0.5 mm in the anterior-posterior direction and 0.4 mm in the superior-inferior direction. The mean values and corresponding standard deviations were 0.07 ± 0.12, -0.05 ± 0.25, and -0.12±0.14 mm for the planes described above. With an 80 kg phantom on the couch, the maximum translation shift was 0.69 mm. The couch walk translation shifts were less than 0.1 mm and rotation shifts were less than 0.1 degree. Conclusions: Errors of a new 6DoF couch were tested using CBCT images of a 3D phantom. The rotation errors were less than 0.3 degree and the translation errors were less than or equal to 0.8 mm in each direction. This level of accuracy is warranted for clinical radiotherapy utilization including stereotactic radiosurgery.

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