Experimental determination of thermal neutron fluence around Elekta Versa HD linear accelerator for various photon energies.

A complex neutron spectrum generated along with a useful photon beam imposes an additional radiation protection risk around medical linear accelerators (linac). The thermal neutron component of this complex neutron spectrum formed during different photon modes of operation of Elekta Versa HD linac has been quantified using Indium foil activation technique. The thermal neutron fluence (Φ ) at isocenter for 15 MV, 10 MV and 10 MV FFF beams was found to be 2.

Analysis of Influence of Errors in Angular Settings of Couch and Collimator on the Dosimetric and Radiobiological Parameters in VMAT Plans.

Objective: To evaluate the impact of couch and collimator angular variations on dose volume histogram (DVH), tumour control probability (TCP), and normal tissue complication probability (NTCP) of the volumetric-modulated arc therapy (VMAT) plans.

Methods: Stereotactic radiosurgery and stereotactic body radiation therapy VMAT plans were generated for three different hypothetical planning target volumes (PTVs) that mimic brain metastases, single brain lesion, and single spine lesion. Thirty routine VMAT plans (10 prostate, 10 head and neck, and 10 brain cases) treated in our clinic were also selected for this study.

Analysis of Dosimetric Impacts of Cone Beam Computed Tomography-Based Volumetric Modulated Arc Therapy Planning.

Objective: To quantify the Hounsfield unit (HU) variations between computed tomography (CT) and cone beam CT (CBCT) and study its impact on volumetric modulated arc therapy (VMAT) plans.

Methods: HU number variations in CT and CBCT images were evaluated using the Catphan-504 phantom, and changes in seven different materials within the phantom (air, polymethylpentene, low-density polyethylene, polystyrene, acrylic, Delrin, and Teflon) were studied. The HU variations in half-fan and full-fan modes of CBCT were evaluated.

Effect of fluence smoothing on the quality of intensity-modulated radiation treatment plans.

A fluence-smoothing function applied for reducing the complexity of a treatment plan is an optional requirement in the inverse planning optimization algorithm of intensity-modulated radiation therapy (IMRT). In this study, we investigated the consequences of fluence smoothing on the quality of highly complex and inhomogeneous plans in a treatment-planning system, Eclipse™. The smoothing function was applied both in the direction of leaf travel (X) and perpendicular to leaf travel (Y).