Room: Exhibit Hall | Forum 8
Purpose: The purpose of this study was to evaluate the image quality of electronic portal imaging using 2.5 MV X-ray.
Methods: The image quality of electronic portal imaging using 2.5 MV X-ray was assessed by physical and visual evaluation. Physical evaluation parameters included contrast, contrast to noise ratio (CNR), and modulation transfer function (MTF), while the Contrast-Detail curve and Image Quality Figure Inverse (IQFinv) were assessed for visual evaluation. For the physical evaluation, images of MV-QA phantom (Varian) and tungsten plate (Toshiba Materials) at STD 100 cm were acquired with Varian TrueBeam using 20 cm Ã— 26.6 cm field size; â€œHigh Qualityâ€? and â€œLow Doseâ€? mode; 2.5, 4 and 6 MV X-ray. The contrast, CNR, and MTF were evaluated using image analysis software, DoseLab (Mobius) and Image J (NIH). For the visual evaluation, images of Las Vegas phantom (Varian) at SSD 100 cm were acquired under the same conditions as used for the physical evaluation, and were assessed by 4 radiological technologists. The Contrast-Detail curve and IQFinv were calculated from the minimum signal diameters detected with 50% confidence for each signal depth.
Results: In comparison with 4 and 6 MV X-ray in â€œHigh Qualityâ€? mode, the contrast of 2.5 MV X-ray was significantly higher by 228% and 307%, respectively. Similarly, the CNR of 2.5 MV X-ray was significantly higher by 37% and 59%, respectively. The resolution of 2.5 MV X-ray for 10% MTF was higher by 104% and 121%, respectively. The Contrast-detail curve and IQFinv of 2.5 MV X-ray were improved. The results in â€œLow Doseâ€? mode showed the same tendency as in the â€œHigh Qualityâ€? mode.
Conclusion: The image quality of electronic portal imaging using 2.5 MV X-ray was better compared to 4 and 6 MV-X-ray.
Radiation Therapy, Portal Imaging, Radiography