Linking dose delivery accuracy and planning target margin in radiosurgery based on dose-volume histograms derived from measurement-guided dose reconstruction

• Published in: Physics in medicine & biology Vol. 64; no. 4; pp. 45009 - 45024
• Main Authors: Chan, Mark K H, Leung, Ronnie W K, Lee, Venus W Y, Wong, Matthew Y P, Chiang, Chi-Leung, Law, Gilbert M L, Blanck, Oliver
• Format: Journal Article
• Language: English
• Published: England IOP Publishing 11.02.2019
• Subjects: Arteriovenous Malformations - pathology; Arteriovenous Malformations - surgery; dose delivery quality assurance; Humans; measurement-guided dose reconstruction; Meningeal Neoplasms - pathology; Meningeal Neoplasms - surgery; Meningioma - pathology; Meningioma - surgery; Neuroma, Acoustic - pathology; Neuroma, Acoustic - surgery; Phantoms, Imaging; planning target margin; qausi-3D dosimetry; radiosurgery; Radiosurgery - methods; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Intensity-Modulated - methods; Surgery, Computer-Assisted - methods
• ISSN: 0031-9155; 1361-6560; 1361-6560
• DOI: 10.1088/1361-6560/aafd47

In radiosurgery (SRS), the geometric uncertainties of machine-related delivery including image-guidance and hence the planning target volume (PTV) are often evaluated by the end-to-end gamma (γ) comparison that carries no information about the clinical relevance of deviations of individual SRS plans during delivery quality assurance (DQA). A proof-of-concept method was proposed to derive the PTV against both the plan- and the machine-specific delivery errors directly from the clinically relevant dose-volume histograms (DVHs) using measured-guided dose reconstruction (MGDR) during DQA. A liquid-filled detector array and a rotating phantom were used to measure sixteen arc-based radiosurgery treatments with 1 and 2 mm gross tumor volume (GTV)-to-PTV margins, producing MGDR-3D dose distribution on both the phantom and the patient CT for γ index and clinical DVH evaluations, respectively. The PTV was considered optimal when the MGDR showed the desired prescription dose coverage (Vpres) of the GTV (100% in this study). Associations of the binary Vpres outcomes (<or  =100%) of the GTV with the acceptance level of percent γ pass rate (γPR%) at 90 versus 95% were assessed. Further receiver operator characteristic (ROC) analysis was performed to assess the distance-to-agreement (DTA) and local dose difference (ΔD) criteria that may be suitable for treatment acceptance. From the MGDR, 100% GTV Vpres was achieved in 68.8% and 100% of plans with 1 and 2 mm PTV, respectively. Vpres outcomes were neither associated with γPR% at 1-2 mm DTA and 1%-3% ΔD nor the acceptance level for MGDR in the patient CT. ROC analysis shows statistically significant AUC values from 0.78-0.84 and 0.79-0.80 for MGDR phantom and patient doses, respectively. DQA by MGDR-DVH objectives offers the unique opportunity of direct assessment of the dose delivery accuracy and hence the optimal PTV without subject to the statistical correlation between γPR% and clinical metrics. Based on multi-criteria DVH objectives, clinical decision can be instantly made to adjust the treatment plan prescription.