Rotational positional error-corrected linear set-up margin calculation technique for lung stereotactic body radiotherapy in a dual imaging environment of 4-D cone beam CT and ExacTrac stereoscopic imaging

Objective Accurate calculation of set-up margin is a prerequisite to arrive at the most optimal clinical to planning target volume margin. The aim of this study was to evaluate the compatibility of different on-board and in-room stereoscopic imaging modalities by calculating the set-up margins (SM)...

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Bibliographic Details
Published in:Radiologia medica 2021-07, Vol.126 (7), p.979-988
Main Authors: Sarkar, Biplab, Ganesh, Tharmarnadar, Munshi, Anusheel, Manikandan, Arjunan, Roy, Soumya, Krishnankutty, Saneg, Chitral, Latika, Sathiya, Jean, Pradhan, Anirudh, Mohanti, Bidhu Kalyan
Format: Article
Language:English
Subjects:
Compatibility
Computed tomography
Diagnostic Radiology
Error correction
Image acquisition
Imaging
Imaging techniques
Interventional Radiology
Mathematical analysis
Medical imaging
Medicine
Medicine & Public Health
Neuroradiology
Oncology Imaging
Radiation therapy
Radiology
Stereoscopy
Ultrasound
X ray imagery
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Summary:Objective Accurate calculation of set-up margin is a prerequisite to arrive at the most optimal clinical to planning target volume margin. The aim of this study was to evaluate the compatibility of different on-board and in-room stereoscopic imaging modalities by calculating the set-up margins (SM) in stereotactic body radiotherapy technique accounting and unaccounting for rotational positional errors (PE). Further, we calculated separate SMs one based on residual positional errors and another based on residual + intrafraction positional errors from the imaging data obtained in a dual imaging environment. Materials and methods A total of 22 lung cancer patients were included in this study. For primary image guidance, four-dimensional cone beam computed tomography (4-D CBCT) was used and stereoscopic ExacTrac was used as the auxiliary imaging. Following table position correction (TPC) based on the initial 4-D CBCT, another 4-D CBCT (post-TPC) and a pair of stereoscopic ExacTrac images were obtained. Further, during the treatment delivery, a series of ExacTrac images were acquired to identify the intrafraction PE. If a, b and c were the observed translational shifts in lateral (x-axis), longitudinal (y-axis) and vertical direction (z-axis) and α, β and γ were the rotational shifts in radians about the same axes, respectively, then the resultant translational vectors (A, B and C) were calculated on the basis of translational and rotational values. Set-up margins were calculated using residual errors post-TPC only and also using intrafraction positional errors in addition to the residual errors. Results Residual and residual + intrafraction SM were calculated from a dataset of 82 CBCTs and 189 ExacTrac imaging sessions. CBCT-based mean ± SD shifts in translational and rotational directions were 0.3 ± 1.8 mm, 0.1 ± 1.8 mm, − 0.4 ± 1.6 mm, 0.1 ± 0.4°, 0.0 ± 1.0° and 0.3 ± 0.7°, respectively, and for ExacTrac − 0.1 ± 1.8 mm, 0.2 ± 2.4 mm, − 0.6 ± 1.8 mm, 0.1 ± 1.2°, − 0.2 ± 1.3° and − 0.1 ± 0.6°, respectively. Residual SM without considering the rotational correction in x, y and z directions were 5.0 mm, 4.5 mm and 4.4 mm; rotation-corrected SM were 4.4 mm, 4.0 mm and 5.5 mm, respectively. Residual plus intrafraction SM were 5.5 mm, 6.6 mm and 6.2 mm without considering the rotational corrections, whereas they were 5.0 mm, 6.3 mm and 6.2 mm with rotational errors accounted for. Conclusion Accurate calculation of set-up margin is required to find the clinical to p
ISSN:0033-8362
1826-6983
DOI:10.1007/s11547-021-01355-7