SU‐E‐T‐123: Development of a Methodology to Assess the Image Quality of the ExacTracTM Localization System Using the PIPSproTM Software and Unfors RaySafe Xi R/F Detector

Purpose: To develop a methodology of assessing and evaluating the consistency of the spatial resolution, dose, energy, noise, contrast, and geometrical accuracy of the BrainLab ExacTrac™ system. Methods: A device was constructed to hold the QCkV‐1 Phantom firmly and reproducibly against the face of the flat panel detectors. Two image sets per detector were acquired using the ExacTrac present console setting‐‐Cranial Standard. The two image sets were analyzed in PIPSpro™ and the following metrics were recorded: spatial resolution (f₃₀, f₄₀, f₅₀), noise and Contrast‐to‐Noise Ratio. Geometrical image accuracy was evaluated by assessing the length of QCkV‐1. Dose and kVp were recorded using the Unfors RaySafe Xi R/F Detector. The kVp and dose were evaluated for the following: Cranial (80kV,80mA,80ms), Thorax (120kV,160mA,160ms), Abdomen (120kV,160mA,130ms) and Pelvis(120kV,160mA,160ms). Results: With regards to spatial resolution, the mean values of the f₃₀, f₄₀ and f₅₀ for the left detector were, 1.39±0.09, 1.24±0.10 and 1.15±0.07 respectively, while the right detector were 1.38±0.07, 1.22±0.08 and 1.13±0.10, respectively. Mean CNR for the left and right detectors was 114±10 and 116±13, respectively. For geometrical accuracy, both detectors had a measured image length of the QCkV‐1 of 218.8±0.3mm. The left detector showed dose measurements of 1.37±0.01 mGy (CS), 12.56±0.03 mGy (TS), 10.08±0.04 mGy (AS) and 12.58±0.05 mGy (PS) while the right detector showed 1.27±0.01 mGy (CS), 11.48±0.03 mGy (TS), 9.21±0.04 mGy (AS) and 11.50±0.04 mGy (PS), respectively. For energy, the left detector had kVp readings of 81.2±0.3 (CS), 121.1±0.4 (TS), 121.0±0.3 (AS) and 121.0±0.3 (PS) and the right detector had 79.9±0.1 (CS), 117.2±0.2 (TS), 117.2±0.2 (AS) and 117.2±0.2 (PS). Conclusion: A methodology was developed to assess the basic image quality parameters recommended by TG‐142 for the ExacTrac™ system. The ExacTrac system shows a consistent dose, kVp, spatial resolution, CNR and geometrical accuracy for each detector over the evaluated timeframe.