Flat-panel detectors using amorphous silicon p-i-n diodes have been developed for chest and therapeutic portal imaging. In radiation therapy, an imaging device is exposed to a high radiation dose. The radiation damage affects the leakage current of diode and may decrease the whole system performance. In this research, we have investigated the radiation damage to the leakage current of a-Si : H ...

Electronic portal imaging device (EPID) plays an important role in radiation therapy portal imaging, geometric and dosimetric verification. Consistent image quality and stable radiation response is necessary for proper utilization that requires routine quality assurance (QA). A commercial 'EPID QC' phantom weighing 3.8 kg with a dimension of 25 × 25 × 4.8 cm³ is used for EPID QA. This device ha...

The goal of this work was to develop and evaluate an end-to-end test for determining and verifying image-guided radiation therapy setup accuracy relative to the radiation isocenter. This was done by placing a cube phantom with a central tungsten sphere directly on the treatment table and offset from isocenter either by 5.0 mm in the longitudinal, lateral, and vertical dimensions or by a random ...

OBJECTIVE To measure setup error of head and neck neoplasm in radiotherapy and discuss over effects of error on physical dose acting on target region and organs at risk of nasopharynx cancer (NPC) patients treated with intensity modulated radiation therapy (IMRT). METHODS A total of 152 patients who developed head and neck neoplasm and received IMRT were randomly selected. Through comparing d...

Introduction: Electronic portal imaging devices (EPIDs) are fundamentally used for instantaneous verification of the patient set‐up, block shape, and leaf positions during radiation therapy. In radiotherapy, situations arise in which an inclined PTV must be treated mutually with adjacent nodal regions. This methodology is most widely used for matching tangential/lateral breas...

Dosimetric properties of an amorphous silicon electronic portal imaging device (EPID) for verification of dynamic intensity modulated radiation therapy (IMRT) delivery were investigated. The EPID was utilized with continuous frame-averaging during the beam delivery. Properties studied included effect of buildup, dose linearity, field size response, sampling of rapid multileaf collimator (MLC) l...

AIMS AND OBJECTIVES To study the geometric uncertainties in the treatment and evaluate the adequacy of the margins employed for planning target volume (PTV) generation in the treatment of focal conformal radiotherapy (CRT) for patients with brain tumors treated with different head support systems. MATERIALS AND METHODS The study population included 11 patients with brain tumors who were to be...

PURPOSE To measure the interfraction setup variation of patient undergoing intensity-modulated radiation therapy (IMRT) of head and neck cancer. The data was used to define adequate treatment CTV-to-PTV margin. MATERIALS AND METHODS During March to September 2006, data was collected from 9 head and neck cancer patients treated with dynamic IMRT using 6 MV X-ray beam from Varian Clinac 23EX. W...