A phantom based evaluation of the clinical imaging performance of electronic portal imaging devices

Marios K Tzomakas; Vasiliki Peppa; Antigoni Alexiou; Georgios Karakatsanis; Anastasios Episkopakis; Christos Michail; Ioannis Valais; George Fountos; Nektarios Kalyvas; Ioannis S Kandarakis

doi:10.1016/j.heliyon.2023.e21116

A phantom based evaluation of the clinical imaging performance of electronic portal imaging devices

Heliyon. 2023 Oct 17;9(10):e21116. doi: 10.1016/j.heliyon.2023.e21116. eCollection 2023 Oct.

Affiliations

¹ Radiation Physics, Materials Technology and Biomedical Imaging Laboratory, Department of Biomedical Engineering, University of West Attica, Egaleo, 12210 Athens, Greece.
² General Hospital of Athens Alexandra, Department of Radiotherapy, 11528 Athens, Greece.
³ Elekta, 15124 Athens, Greece.
⁴ Medical Physics Laboratory, Medical School, National and Kapodistrian University of Athens, 115 27 Athens, Greece.

Abstract

Purpose: In this study an evaluation of the imaging performance of an electronic portal imaging device (EPID) is presented. The evaluation performed employing the QC-3V image quality phantom.

Methods: An EPID system of a 6 MV LINAC, was used to obtain images of a QC-3V EPID phantom. The X-ray source to phantom distance was 100 cm and the field size was 15x15 cm². The irradiation conditions comprised Dose Rates (DR) of 200, 400 and 600 for a 2 MU-100 MU range. The Contrast Transfer Function (CTF), the Noise Power Spectrum (NPS), the Normalized Noise Power Spectrum (NNPS) and the Contrast-to-Noise Ratio (CNR) were studied. In addition, an alternative factor showing a frequency related output signal-to-noise ratio (SNR), the Signal-to-Noise-Frequency Response (SNFR), has been introduced. SNFR is a comprehensive quality index, easily determined in clinical environment.

Results: The CTF curves were found comparable to each other. The lowest values were measured at 2 MU and 200 MU/min. Concerning the NPS and NNPS graphs it was found that the values decrease up to approximately 0.3 lp/mm and demonstrate a white noise shape afterwards. SNFR values were found reducing with spatial frequency. Highest CNR were found between the region 7 and 11 of the phantom.

Conclusions: The influence of MU and DR on EPID performance were investigated. Image quality was assessed using the QC-3V phantom. The presented results can lead to image quality amelioration and act supportively to current image quality control routine protocols.

Keywords: Detector; EPID; Image quality; Phantom; QC-3V.