(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: to investigate the effect of 4DCT cine imaging parameters on the patient dose and image accuracy for lung patient with extremely long breathing cycles.
Methods: A GE Lightspeed RT16 CT system is used to acquire cine 4DCT images on a CIRS lung phantom. The CIRS phantom is set to simulate sinusoid breathing motion with cycles up to 10 s presented in a lung cancer patient. The image acquisition parameters such as gantry rotation speed, sli ce and cine time are adjusted to acquire a complete 4DCT images. The kVp of the x-ray tube is kept to 120 kV unchanged. The filament current changed following the workstation default values which have the same mAs for a single full gantry rotation. The imaging dose for a full 4DCT is measured by placing a CT 10 cm cylindrical ionization chamber (RaySafe X2 CT sensor) to the central channel of a CTDI10 head phantom. The phantom is irritated at central position with a single cine scan of 2 cm collimation.
Results: Our study shows that the imaging dose for a single bed position 4DCT decreased nearly to a half of that when the gantry speed is slowed down from 0.5 s to 1.0 s for a 10 s breathing cycle patient. The imaging dose keeps unchanged when the cine time between images varies from 0.5 s to 1.0 s. Image quality will focus on the studies of noise features and geometry accuracy with respect to the gantry rotation speed.
Conclusion: Our preliminary study demonstrated that a 4DCT protocol with a slow gantry rotation speed is in favored for 10 s breathing cycle patient in terms of imaging dose with acceptable imaging quality compromise.
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