SU-E-J-82: Evaluation of the Spatial Reproducibility and Temporal Drift of the CRAD CatalystHD System.

INTRODUCTION: With the implementation of new nonradiographic imaging technologies, system performance characterization is crucial prior to clinical implementation.In this study, the short-term static, spatial reproducibility and temporal drift of the CatalystHD 3-camera nonradiographic imaging system were evaluated.

METHODS: Using the CatalystHD Daily Check phantom aligned to the room lasers, both the spatial reproducibility and temporal drift were analyzed in the treatment room with low ambient light (12.65lx)and full light (236.25lx).For temporal drift, measurements were acquired every 5min after cold initialization for 60min without altering the position of the phantom.Prior to the initial measurement, cameras were off for a minimum of 24hours.For spatial reproducibility, a series of 30 sequential measurements were acquired over a 25min period after the system had been on for more than 3 hours without adjusting the Daily Check phantom.For both tests, spatial location of the phantom determined by the CatalystHD system was recorded

RESULTS: For temporal drift, total displacement vectors and equilibrium times were calculated for each camera.Displacement vectors were normalized to a value long after equilibrium had been achieved.For the middle camera in low light, ΔX,ΔY,ΔZ,Δ3D were 0.2,0.8,0.1and 0.9 mm, respectively.For full light, ΔX,ΔY,ΔZ,Δ3D were 0.2,1.0,0.1and 1.1 mm, respectively.Both the left and right camera responded similarly.The equilibrium time in low light was 35,45,and 45 minutes for the left, middle and right cameras, respectively, while in full light, they were 30,45,and 40 minutes.For spatial reproducibility in low light, the STD of the recorded locations were 0.04,0.02,0.03mm for the left, middle and right cameras, respectively.For full light, deviations of 0.03,0.02and 0.03 were recorded. Maximum recorded range for any deviation was 0.14mm-below system specification of 0.2mm.

CONCLUSION: A study was performed to assess the spatial reproducibility and temporal drift of the CatalystHD as recommended by TG-147 for nonradiographic imaging systems.An overall warmup time of at least 45 minutes is recommended prior to use. 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.