Document Type : Original Paper
Department of Radiotherapy and Oncology, Rural Medical College, Pravara Institute of Medical Sciences (PIMS), Loni, Maharashtra; India
Government Cancer Hospital, Mahatma Gandhi Memorial Medical College, Indore, Madhya Pradesh; India
Introduction: State-of-art radiotherapy technique as Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are being used to treat cancer with high accuracy. Verification of planned and delivered dose distribution is critical; in this study we evaluated quality assurance (QA) results and effectiveness of Electronic Portal Imaging Device (EPID) and IMatriXX.
Material and Methods: Performance of EPID and IMatriXX was assessed with dose measurements using ionization chamber. Calibrated IMatriXX and EPID are used for pre-treatment patient-specific quality assurance (PSQA) for 204 patients plans with IMRT treatment technique on LINAC. Dose image were compared for gamma evaluation (3%/3mm) and combination of three scalar parameters were assessed against EPID to quantify gamma results within region of interest; namely average g(gavg), maximum g(gmax) and Area Gamma<1.
Results: The g correlation comparisons yielded an average correlation of 0.991 for IMatriXX and 0.978 for EPID. The maximum gamma value is 0.99, while the minimum gamma is 0.872 for IMatriXX and 0.926 for EPID, which can be used as baseline. Our result suggests that EPID dosimetry, provides lower gamma correlation values than IMatriXX. Students Unpaired t-Test analysis was applied to two data sets. The calculated p-value 0.001 shows good correlation.
Conclusion: The EPID and IMatriXX have significantly improved dosimetric properties, providing more sensitive, accurate pre-treatment PSQA. The result shows EPID can replace other 2D dosimetry methods and ionization chamber measurements. It’s an efficient, sensitive and accurate dosimetry tool and is primary protocol of pre-treatment quality assurance.