The main objectives of this study are to (1) analyze the sensitivity of various gamma index passing rates using different types of detectors having different resolutions and (2) investigate the sensitivity of various gamma criteria in intensity-modulated radiation therapy (IMRT) and volumetrically modulated arc therapy (VMAT) quality assurance (QA) for the detection of systematic multileaf coll...

BACKGROUND In volumetric modulated arc therapy (VMAT), gantry angles, dose rate and the MLC positions vary with the radiation delivery. The quality assurance (QA) system should be able to catch the planning and machine errors. The aim of this study was to investigate the sensitivity of three VMAT QA systems to machine errors. METHODS Several types of potential linac machine errors unique to V...

abstractbackground: although electronic portal imaging devices (epids) have originally developed for positioning verification, they can also be used for dosimetric purposes. in the current work, the dose response of minimum detectable thickness of a scanning liquid filled ion chamber epid, slic-epid, and the variation of transmitted dose with the shift of inhomogeneity inside of phantom was als...

Patient-specific quality assurance for intensity-modulated radiation therapy (IMRT) dose verification is essential. The aim of this study is to provide a new method based on the relative error distribution by comparing the fluence map from the treatment planning system (TPS) and the incident fluence deconvolved from the electronic portal imaging device (EPID) images. This method is validated fo...

Estimates of association from nonrandomized epidemiologic studies are susceptible to two types of error: random error and systematic error. Random error, or sampling error, is often called chance, and decreases toward zero as the sample size increases and the data are more efficiently distributed in the categories of the adjustment variables. The amount of random error in an estimate of associa...

 ABSTRACTBackground: Although Electronic Portal imaging Devices (EPIDs) have originally developed for positioning verification, they can also be used for dosimetric purposes. In the current work, the dose response of minimum detectable thickness of a Scanning Liquid filled Ion Chamber EPID, SLIC-EPID, and the variation of transmitted dose with the shift of inhomogeneity inside of phantom was al...

[1] This study contributes to characterization of satellite precipitation error which is fundamental to develop uncertainty models and bias reduction algorithms. Systematic and random error components of several satellite precipitation products are investigated over different seasons, thresholds and temporal accumulations. The analyses show that the spatial distribution of systematic error has ...

BACKGROUND The reproducibility of patient setup for radiotherapy is based on various methods including external markers, X-rays with planar or computerized image acquisition, and, more recently, surface matching imaging. We analyzed the setup reproducibility of 16 patients affected by prostate cancer who underwent conformal radiotherapy with curative intent by using a surface image registration...

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...