Room: Exhibit Hall | Forum 5
Purpose: To investigate the reduction of respiratory motion artifacts using a volumetric 4D-CT (v4D-CT) scanner.
Methods: The GE 256-slice Revolution CT scanner was used to acquire v4D-CT images of the Quasar Respiratory Motion Phantom (Modus Medical Devices, London, Canada) with a cedar insert containing three polystyrene spheres (30mm, 20mm, 10mm diameter) which moved in a sinusoidal pattern at 0.25 cycles/s and 2.5cm amplitude. Gold markers were embedded within one of the spheres. Images were acquired in axial mode at a single bed position (140 mm axial field-of-view (AFOV), 0.28s/revolution, 0.88s between images, 52s scan time, 120kVp, 10mA, 2.5mm slices). The images were binned into 10 respiratory phases and averaged to recover the signal-to-noise ratio. The motion of the markers was tracked, their volumes determined, and mean CT number in the static acrylic portion of the phantom was calculated at each phase. v4D-CT images of a sedated and ventilated pig were also acquired (120mm AFOV, 0.5s/revolution, 5mm slice thickness) and analyzed for motion artifacts.
Results: Phantom motion was recovered for the entire 52s acquisition, and was strongly correlated with the known motion trace using the Pearson Correlation Coefficient (r=0.996,p<.001). The CT number measured in a single image was (128+/-29) HU and after binning was (127+/-13) HU, indicating a decrease in noise. Three spheres (30mm, 20mm and 10mm diameter) were contoured, and the measured diameter was in agreement within 5% of the known diameter for all phases: 30.0+/-0.4mm, 20.6+/-0.3mm, and 10.5+/-0.5mm, respectively, indicating that there were no motion artifacts. In the porcine images the lung, heart, diaphragm and liver were imaged though all phases of the breathing cycle in the 120mm AFOV with no visible motion artifacts.
Conclusion: v4D-CT may allow for fast acquisition of artifact-free 4D-CT images with accurate CT number, and for improved estimation of respiratory motion over time.