SU-E-J-50: An Evaluation of the Stability of Image Quality Parameters of the Elekta XVI and IView Imaging Systems

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Abstract

Introduction

Quality assurance of the image quality for image guided localization systems is crucial to ensure accurate visualization and localization of target volumes. In this study, the long term stability of selected image parameters was assessed and evaluated for CBCT mode, planar radiographic kV mode and MV mode. Methods and Materials: The 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) 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.

Results

A total of 20 and 10 measurements were acquired for the planar radiographic and CBCT systems respectively over a two month period. Values were normalized to the mean and the standard deviations (STD) were recorded. For the planar radiographic spatial resolution, the STD for f30, f40, f50 were 0.004, 0.002, 0.002 and 0.005, 0.007, 0.008 for the kV and MV, respectively. The average recorded dose for kV was 38.7±2.7 μGy. The STD of the evaluated metrics for the S20 acquisition were: 0.444(f30), 0.067(f40), 0.062(f50), 0.018(Water/poly-HU constancy), 0.028(uniformity) and 0.106(noise). The standard deviations for the M20 acquisition were: 0.108(f30), 0.073(f40), 0.091(f50), 0.008(Water/poly-HU constancy), 0.005(uniformity) and 0.005(noise). Using these, tolerances can be reported as a warning and action threshold of 1σ and 2σ.

Conclusion

A study was performed to assess the stability of the basic image quality parameters recommended by TG-142 for the Elekta XVI and iView imaging systems. Consistent imaging and dosimetric properties over the evaluated time frame were noted.

This work was funded in part by the Cancer Prevention Research Institute of Texas Pre doctoral fellowship training grant (RP140105) to Dennis N. Stanley M.Sc.

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