Evaluation of CBCT based dose calculation in the thorax and pelvis using two generic algorithms. (November 2022)

• Record Type: Journal Article
• Authors: Thing, R.S.; Nilsson, R.; Andersson, S.; Berg, M.; Lund, M.D.
• Is Part Of: Physica medica. Volume 103(2022)
• Page Start: 157
• Page End: 165
• Publication Date: 2022-11
• Subjects: Cone beam CT -- Artefact correction -- Deformable image registration -- Adaptive radiotherapy; 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.2022.10.012
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract: Purpose: This work examines the dosimetric performance of two algorithms creating a corrected CBCT (corrCBCT) and a virtual CT (vCT) implemented in a commercial treatment planning system. Methods: 60 patients distributed across all patient groups treated with curative intent at Vejle Hospital (breast, lung, prostate and anal/rectal cancer) were selected for the present study. Clinical treatment plans were recalculated on corrCBCT and vCT, as well as a reference CT (refCT) acquired as close in time to the CBCT image as possible. Recalculated doses were compared using gamma analysis, as well as by comparing D 98 %, D 50 %, and D 2 % for all delineated targets and organs at risk. Results: High dosimetric accuracy is demonstrated on both the corrCBCT and vCT. Gamma 2 % / 2 mm pass rates > 98 % were found for all patients except two outliers still having > 93 % pass rates. Equivalence of all evaluated dose metrics within ± 1 Gy was observed for all patient groups, while the pelvic patients additionally showed equivalence for all metrics within ± 1 % of the refCT dose. For the thoracic patients, equivalence within ± 2 . 5 % was established for all metrics except median dose to the ipsilateral lung, calculated on corrCBCT for the breast patient group. Conclusion: The corrCBCT and vCT images are shown in excellent dosimetric agreement with refCT images, and show high potential for future use for streamlined adaptive radiotherapy workflows. Highlights: Accurate CBCT based dose calculation is demonstrated using two different algorithms. Both algorithms perform only post-processing and are CBCT-vendor agnostic. Dose calculation accuracy is evaluated on 20 thoracic and 40 pelvic patients. Gamma 2%/2 mm pass rates above 98% is shown for 58/60 patients. Equivalence to CT-based dose within 1 Gy is shown for all evaluated dose metrics.