An evaluation of the stability of image quality parameters of Elekta X‐ray volume imager and iViewGT imaging systems

Abstract

IntroductionA robust image quality assurance and analysis methodology for image‐guided localization systems is crucial to ensure the accurate localization and visualization of target tumors. In this study, the long‐term stability of selected image parameters was assessed and evaluated for the cone‐beam computed tomography (CBCT) mode, planar radiographic kV mode, and the radiographic MV mode of an Elekta VersaHD.Materials and MethodsThe CATPHAN, QckV‐1, and QC‐3 phantoms were used to evaluate the image quality parameters. The planar radiographic images were analyzed in PIPSpro™ with spatial resolution (f30, f40, f50), contrast to noise ratio (CNR) and noise being recorded. For XVI CBCT, Head and Neck Small20 (S20) and Pelvis Medium20 (M20) standard acquisition modes were evaluated for uniformity, noise, spatial resolution, and HU constancy. Dose and kVp for the XVI were recorded using the Unfors RaySafe Xi system with the R/F low detector for the kV planar radiographic mode. For each metric, values were normalized to the mean and the standard deviations were recorded.ResultsA total of 30 measurements were performed on a single Elekta VersaHD linear accelerator over an 18‐month period without significant adjustment or recalibration to the XVI or iViewGT systems during the evaluated time frame. For the planar radiographic spatial resolution, the normalized standard deviation values of the f30, f40, and f50 were 0.004, 0.003, and 0.003 and 0.015, 0.009, and 0.017 for kV and MV, respectively. The average recorded dose for kV was 67.96 μGy. The standard deviations of the evaluated metrics for the S20 acquisition were 0.083(f30), 0.058(f40), 0.056(f50), 0.021(Water/poly‐HU constancy), 0.029(uniformity) and 0.028(noise). The standard deviations for the M20 acquisition were 0.093(f30), 0.043(f40), 0.037(f50), 0.016(Water/poly‐HU constancy), 0.010(uniformity) and 0.011(Noise).ConclusionA study was performed to assess the stability of the basic image quality parameters recommended by TG‐142 for the Elekta XVI and iViewGT imaging systems. The two systems show consistent imaging and dosimetric properties over the evaluated time frame.

Development and long‐term stability of a comprehensive daily QA program for a modern pencil beam scanning (PBS) proton therapy delivery system

“…For example, there have been publications characterizing the impact of spot size on treatment plan quality . A third approach is to use statistical process control to evaluate whether specific parameters are behaving in a stable and controlled manner . With this information, it is possible to use statistical methods to determine the system specific action level tolerances due to the system performance.…”

Determination of machine‐specific tolerances using statistical process control analysis of long‐term uniform scanning proton machine QA results

“…The application of SPC to control charts allows users to assess the temporal stability of each test parameter and determine whether the various parameters of the system are in statistical control. [2][3][4][5][6] Literature [2][3][4] has reported using control limits at AE3σ for detecting meaningful changes in system performance. The SPC helps in monitoring the process using the control charts, which are used to distinguish between the common and special cause variations.…”

“…The SPC helps in monitoring the process using the control charts, which are used to distinguish between the common and special cause variations. [2][3][4] Several studies [2][3][4][5][6][7][8][9][10][11] highlighted the importance of using SPC analysis in the radiotherapy department. For instance, Binny et al 2,7 used the SPC to evaluate the beam output and symmetry of the linear accelerators.…”

“…For instance, Binny et al 2,7 used the SPC to evaluate the beam output and symmetry of the linear accelerators. Shiraishi et al 11 and Stanley et al 5,6 assessed the stability of image quality parameters using SPC. The authors observed the application of SPC in conventional photon therapy, but the literature on SPC analysis in proton therapy is limited.…”