146. Comparing group based and patient specific cone-beam CT intensity correction methods for VMAT dose recalculations. (December 2018)

• Record Type: Journal Article
• Authors: Fidanzio, A.; De Spirito, M.; Mirri, M.A.; Consorti, R.; Mangiacotti, F.; Petrucci, A.
• Is Part Of: Physica medica. Volume 56(2018)Supplement 2
• Page Start: 155
• Publication Date: 2018-12
• Subjects: 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.2018.04.157
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: The aim of this work was to compare two approaches of cone-beam computed tomography (CBCT) image intensity-correction for dose recalculation of volumetric arc radiotherapy (VMAT) plans. Methods and materials: CBCT-based dose calculation accuracy was assessed for pelvic, lung, and head and neck (H&N) treatment sites. The dose distributions of 10 patients for each body regions were re-calculated by RayStation (RS) and Eclipse treatment planning systems (TPS). In particular CBCT RS were calibrated by patient specific density assignment method supplied by RS TPS, while CBCT ROI, obtained applying ROI-based lookup tables for each body region were used in Eclipse TPS. Dose Volume Histogram (DVH) statistics and 3D γ -analysis (3%, 3 mm) of the dose maps and dose-volume statistics were determined to compare the CBCT dose distributions with those of the planning CTs in absence of morphological changes. Results: The results indicate a comparable performance of both intensity correction techniques in the scope of VMAT. The differences in the investigated DVH parameters with respect to the pCT were mostly below 2% for both methods, however the γ -index analysis, being more sensitive to local dose changes, pointed out slight inaccuracies in the CBCT ROI dose distributions with respect to CBCTRS . In particular γ -index pass-rates were found increased for CBCTRS with respect to CBCTROI in pelvic (98% against 95%) in lung (97% against 93%) and in H&N (99% against 95%). Conclusion: Both the CBCT intensity correction approaches are attractive options for CBCT dose recalculation and in vivo dose reconstructions[1, 2] . No added value was found by using a patient-specific HU table, showing similar results as the group based HU tables in terms of DVH indices while the γ -analysis showed better results for CBCTRS .