On the pitfalls of PTV in lung SBRT using type-B dose engine: an analysis of PTV and worst case scenario concepts for treatment plan optimization.

Background: PTV concept is presumed to introduce excessive and inconsistent GTV dose in lung stereotactic body radiotherapy (SBRT). That GTV median dose prescription (D) and robust optimization are viable PTV-free solution (ICRU 91 report) to harmonize the GTV dose was investigated by comparisons with PTV-based SBRT plans.

Methods: Thirteen SBRT plans were optimized for 54 Gy / 3 fractions and prescribed (i) to 95% of the PTV (D) expanded 5 mm from the ITV on the averaged intensity project (AIP) CT, i.

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

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.

Feasibility study of robotic hypofractionated lung radiotherapy by individualized internal target volume and XSight Spine Tracking: a preliminary dosimetric evaluation.

Aim: To investigate the dosimetric impacts of lung tumor motion in robotic hypofractionated radiotherapy for lung cancers delivered through continuous tracking of the vertebrae by the XSight Spine Tracking (XST) mode of the CyberKnife.

Materials And Methods: Four-dimensional computed tomography (4DCT) scans of a dynamic thorax phantom were acquired. Three motion patterns (one-dimensional and three-dimensional) of different range were investigated.