Quality assurance of geometric accuracy based on an electronic portal imaging device and log data analysis for Dynamic WaveArc irradiation

AbstractPurpose:The main objective of this study is to assure the quality of cervical cancer treatment plans using an electronic portal imaging device (EPID) in RapidArc techniques.Materials and Methods:Fifteen cases of cervical cancer patients undergoing RapidArc technique were selected to evaluate the quality assurance (QA) of their treatment. The computed tomography (CT) of each patient was obtained with 3-mm-slice thickness and transferred to the Eclipse treatment planning system. The prescribed dose (PD) of 50·4 Gy with 1·8 Gy per fraction to planning target volume (PTV) was used for each patient. The aim of treatment planning was to achieve 95% of PD to cover 97%, and dose to the PTV should not receive 105% of the PD. All RapidArc plans were created using the AAA algorithm and treated on Varian DHX using 6 MV photon beam, with two full arcs. Gamma analysis was used to evaluate the quality of the treatment plans with accepting criteria of 95% at 3%/3 mm.Results:In this study, maximum and average gamma values were 2·53 ± 0·409 and 0·195 ± 0·059 showing very small deviation and indicating the smaller difference between both predicted and portal doses. Gamma Area changes from > 0·8 to > 1·2. SD increased to 5·4% and mean standard error increased to 4·67%.Conclusion:On the basis of these outcomes, we can summarise that the EPID is a useful tool for QA in standardising and evaluating RapidArc treatment plans of cervical cancer in routine clinical practice.

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Quality assurance of linear accelerator: a comprehensive system using electronic portal imaging device

Journal of Radiotherapy in Practice ◽

10.1017/s146039691800050x ◽

2018 ◽

Vol 18 (02) ◽

pp. 138-149

Author(s):

P. Niyas ◽

K. K. Abdullah ◽

M. P. Noufal ◽

R. Vysakh

Keyword(s):

Quality Assurance ◽

Linear Accelerator ◽

Planning System ◽

Treatment Planning System ◽

Patient Specific ◽

Array Detector ◽

Electronic Portal Imaging Device ◽

Imaging Device ◽

Portal Imaging ◽

Electronic Portal Imaging

AbstractAimThe Electronic Portal Imaging Device (EPID), primarily used for patient setup during radiotherapy sessions is also used for dosimetric measurements. In the present study, the feasibility of EPID in both machine and patient-specific quality assurance (QA) are investigated. We have developed a comprehensive software tool for effective utilisation of EPID in our institutional QA protocol.Materials and methodsPortal Vision aS1000, amorphous silicon portal detector attached to Clinac iX—Linear Accelerator (LINAC) was used to measure daily profile and output constancy, various Multi-Leaf Collimator (MLC) checks and patient plan verification. Different QA plans were generated with the help of Eclipse Treatment Planning System (TPS) and MLC shaper software. The indigenously developed MATLAB programs were used for image analysis. Flatness, symmetry, output constancy, Field Width at Half Maximum (FWHM) and fluence comparison were studied from images obtained from TPS and EPID dosimetry.ResultsThe 3 years institutional data of profile constancy and patient-specific QA measured using EPID were found within the acceptable limits. The daily output of photon beam correlated with the output obtained through solid phantom measurements. The Pearson correlation coefficients are 0.941 (p = 0.0001), 0.888 (p = 0.0188) and 0.917 (p = 0.0007) for the years of 2014, 2015 and 2016, respectively. The accuracy of MLC for shaping complex treatment fields was studied in terms of FWHM at different portions of various fields, showed good agreement between TPS-generated and EPID-measured MLC positions. The comparison of selected patient plans in EPID with an independent 2D array detector system showed statistically significant correlation between these two systems. Percentage difference between TPS computed and EPID measured fluence maps calculated for number of patients using MATLAB code also exhibited the validity of those plans for treatment.

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