BACKGROUND Traditional CTV-PTV margin recipes are not generally applicable in the situation of stereotactic ablative radiotherapy (SABR) treatments of multiple target volumes with a single isocentre. In this work, we present a novel geometric method of margin derivation based on CBCT-derived anatomical data. METHODS Twenty patients with high-risk localized prostate cancer were selected for re...

PURPOSE The geometrical uncertainties in the patient positioning during intensity modulated radiotherapy (IMRT) are crucial as there is potential to underdose the tumor and overdose the nearby critical structures. Image guided techniques provide a solution to assess the patient set-up uncertainties and help determine the optimal planning target volume (PTV) margin to the clinical tumor volume (...

Recently, intensity-modulated radiation therapy (IMRT) has been used for total-body irradiation (TBI). Since the planning target volume (PTV) for TBI includes the surrounding air, a dose prescription to the PTV provides high fluence to the body surface. Thus with just a small set-up error, the body might be exposed to a high-fluence beam. This study aims to assess which target volume should be ...

By adapting to the actual patient anatomy during treatment, tracked multi-leaf collimator (MLC) treatment deliveries offer an opportunity for margin reduction and healthy tissue sparing. This is assumed to be especially relevant for hypofractionated protocols in which intrafractional motion does not easily average out. In order to confidently deliver tracked treatments with potentially reduced ...

PURPOSE To analyze the distribution of functional liver volume (FLV) in the margin volume (MV) surrounding hepatocellular carcinoma (HCC) with portal vein tumor thrombus (PVTT) before radiation therapy (RT) and to verify the safety of single photon emission computed tomography-based three-dimensional conformal radiotherapy (SPECT-B3DCRT) by exploring the relation of FLV in MV to radiation-induc...

PURPOSE To assess whether online adaptive radiotherapy for bladder cancer is feasible across multiple Radiation Oncology departments using different imaging, delivery and recording technology. MATERIALS AND METHODS A multi-centre feasibility study of online adaptive radiotherapy, using a choice of three "plan of the day", was conducted at 12 departments. Patients with muscle-invasive bladder ...

This study investigated position dependence in planning target volume (PTV)-based and robust optimization plans using full-arc and partial-arc volumetric modulated arc therapy (VMAT). The gantry angles at the periphery, intermediate, and center CTV positions were 181°-180° (full-arc VMAT) and 181°-360° (partial-arc VMAT). A PTV-based optimization plan was defined by 5 mm margin expansion of the...

PURPOSE Setting a proper margin is crucial for not only delivering the required radiation dose to a target volume, but also reducing the unnecessary radiation to the adjacent organs at risk. This study investigated the independent one-dimensional symmetric and asymmetric margins between the clinical target volume (CTV) and the planning target volume (PTV) for linac-based single-fraction framele...

BACKGROUND Reproducibility of different immobilization systems, which may affect set-up errors, remains uncertain. Immobilization systems and their corresponding set-up errors influence the clinical target volume to planning target volume (CTV-PTV) margins and thus may result in undesirable treatment outcomes. This study compared the reproducibility of patient positioning with Hipfix system and...

This study evaluated a method for prostate intensity-modulated radiation therapy (IMRT) based on edge-enhanced (EE) intensity in the presence of intrafraction organ deformation using the data of 37 patients treated with step-and-shoot IMRT. On the assumption that the patient setup error was already accounted for by image guidance, only organ deformation over the treatment course was considered....