PURPOSE By default, the 4-mm wide leaf-pairs of the Elekta Beam Modulator MLC not used for field shaping are moved to under the primary collimator to minimize the leakage dose. The trade-off is the increased beam delivery time in the case of IMRT. This study examines the dosimetric impact and improved delivery efficiency by allowing the unused leaf-pair as 2mm gap to stay within the PTV apertur...

BACKGROUND The aim of this study was to evaluate the performance of a commercial knowledge-based planning system, in volumetric modulated arc therapy for prostate cancer at multiple radiation therapy departments. METHODS In each institute, > 20 cases were assessed. For the knowledge-based planning, the estimated dose (ED) based on geometric and dosimetric information of plans was generated in...

BACKGROUND In this study, we aimed to establish the rabbit VX2 limb tumor model, and then prepare a "necrotic zone" as a safe margin by volumetric modulated arc therapy and simultaneous integrated boost (VMAT-SIB) technique applied in the areas where the tumor is located adjacent to the bone (GTVboost area). MATERIAL AND METHODS Rabbits in the control group (n=10) were not treated, while thos...

the aim of radiation therapy treatment planning is to achieve an optimal balance between delivering a high dose to target volume and a low dose to healthy tissues. in order to refrain any complications resulting from the dose to the surrounding normal organs, the role of treatment plan has been critically evaluated in term of how large the volume or mass of normal tissues exposed in the radiati...

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 (...

BACKGROUND Hypo-fractionated external beam radiotherapy with narrow CTV-PTV margins is increasingly applied for prostate cancer. This demands a precise target definition and knowledge on target location and extension during treatment. It is unclear how increase in fraction size affects changes in prostate volume during treatment. Our aim was to study prostate volume changes during extreme hypo-...

The purpose of this study was to validate the dose prescription defined to the gross tumor volume (GTV) 3D and 4D dose distributions of stereotactic radiotherapy for lung cancer. Treatment plans for 94 patients were generated based on computed tomography (CT) under free breathing. A uniform margin of 8 mm was added to the internal target volume (ITV) to generate the planning target volume (PTV)...

BACKGROUND To assess the dosimetric effect induced by inter-observer variability in target definition for 3D-conformal RT (3DCRT) and volumetric modulated arc therapy by RapidArc (RA) techniques for rectal cancer treatment. METHODS Ten patients with rectal cancer subjected to neo-adjuvant RT were randomly selected from the internal database. Four radiation oncologists independently contoured ...

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...

We have investigated a method to individualize the planning target volume (PTV) for deformable targets in radiotherapy by combining a computer tomography (CT) scan with multiple cone beam (CB)CT scans. All combinations of the CT and up to five initial CBCTs were considered. To exclude translational motion, the clinical target volumes (CTVs) in the CBCTs were matched to the CTV in the CT. PTVs i...