Investigating the robustness of the AlignRT InBore™ co-calibration process and determining the overall tracking errors. (April 2023)

• Record Type: Journal Article
• Authors: Nguyen, Daniel; Khodri, Mustapha; Sporea, Cristina; Reinoso, Rebeca; Jacob, Yannick; Farah, Jad
• Is Part Of: Physica medica. Volume 108(2023)
• Publication Date: 2023-04
• Subjects: AlignRT Inbore™ -- Co-calibration -- MV calibration -- Closed-bore linacs -- SGRT; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2023.102567
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: AlingRT InBore's ceiling and ring-mounted cameras co-calibration to Halcyon. Extrinsic and intrinsic overall calibration errors are determined. MV images-based calibration enables sub-millimetric accuracy. Laser-based calibration is insufficient for breast/SBRT DIBH procedures. Abstract: Objective: To determine the overall tracking errors inherent to the co-calibration procedure of AlignRT InBore™'s (Vision RT Ltd., London, UK) ceiling-mounted and ring-mounted cameras. Methods: Extrinsic calibration errors related to the mismatch between ceiling and InBore cameras' isocentres and treatment isocentre were determined using MV images and the SRS package and compared to traditional plate-based error. Next, using a realistic anthropomorphic female phantom, intrinsic calibration errors were determined while varying source-skin distance (80 to 100 cm), breast board inclination (0° to 12.5°), room lighting conditions (0 to 258 lx), skin colour (dark, white and natural skin colour), and pod occlusion. Results: MV images of the cube proved plate-based calibration to suffer from large errors especially in the vertical direction (up to 2 mm). Intrinsic calibration errors were considerably lower. Indeed, RTD values of ceiling and InBore cameras showed little variability with isocentre depth (within 1.0 mm/0.4°), surface orientation and breast board inclination (within 0.7 mm/0.3°), changing lighting conditions (within 0.1 mm/0.2°), skin colour/tone (within 0.3 mm/0.3°) and camera pod occlusion (within 0.3 mm/0.2°). Conclusion: The use of MV-images proved critical to maintain co-calibrating errors of ceiling and InBore cameras to Halcyon's treatment isocentre below 1 mm.