Sources of Motion Artifacts in 4DCT Reconstruction
B Yi*, W Lu, S Lee, E Hu, C Yu, G Lasio, University of Maryland Medical Center, Baltimore, MDSU-D-WAB-6 Sunday 2:05PM - 3:00PM Room: Wabash Ballroom
Purpose: To identify sources of motion artifacts (MA) in 4-D CT reconstruction when patient breathing is irregular.
Methods: A simulation study with a wire phantom was designed to quantify MA in phase-sorted 4D CT. Motion in the inferior-superior with cos4ωt variation and 1 cm motion range was assumed. Motion frequency, expressed in breaths per minute (BPM) was assumed to be 15 for most of our cases, and always higher than 10 in order to exclude undersampling artifacts due to slow breathing and violate data sufficiency. The simulation included variations in motion period, amplitude and baseline drift; these variations were assumed to be affecting phantom and surrogate motion simultaneously. A varying phase shift between the phantom motion and the surrogate motion was also studied. The effect on MA derived from the variation of the above parameters was evaluated.
Results:No noticeable MA was observed when the breathing period is changing during scanning. Variations of the amplitude and the base line drift play little role in generating MA. MA only becomes noticeable when the variation of the amplitude becomes larger than 30% of the motion range -or 3mm in our simulation. MA, however are sensitive to the variation in the phase difference between surrogate and phantom motion. Change of only 10 degrees in phase or 0.1 seconds shift during scanning generated significant MA.
Conclusion:Change of phase between the breathing surrogate and the organ motion during scanning is the main source of the MA if patient breathing period is not too slow, i.e. if the data sufficiency condition is not violated.
Funding Support, Disclosures, and Conflict of Interest: NIH R01 CA133539