SU-E-J-137: A Theoretical Model for the Analysis of Residual Motion Artifacts in 4D CT Scans.

PURPOSE

The purpose of this study was to analysis the residual motion artifact in 4D-CT scan using a simple one-dimension theoretical model.

METHODS

In order to evaluate the target displacement at each phase image, We used phantom (Dynamic Thorax Phantom, CIRS, Norfolk, VA) which could control programmable regular 1D sine motion and belt type respiratory monitoring system. 2cm diameter spherical target was inserted in the phantom and then we set-up regular 1D sine motion and adjusted three level of amplitude (10, 20, 30 mm) with fixed period (4s). Four dimensional (4D) CT images were acquired by CT scanner (Sensation Open, Siemens Medical Systems, Forchheim, Germany) with a slice thickness of 1.5 mm and 0.1 pitch in helical mode. Respiratory monitoring system (AZ-733V, Anzai MEDICAL) was placed on the abdominal surface of phantom, and the respiratory signal was acquired. CorePLAN (RTP, SC&J) software was used to acquire static target diameter and each ten phase diameters.

RESULTS

The displacements (?S) peak at the 20∼30% or 70∼80% phases, and are minimized at the 50% phase. This is because the target velocity is minimum at 50% phase and maximum at 30 and 70% phases; hence, the large image blur. The measured diameters of target are compared to the simulation results and we observed similar trends of target diameter change.

CONCLUSIONS

In this study, we presented simple one-dimensional model to analyze the residual motion artifact in 4D-CT scan. The model was used to explain the effect of residual motion on each phase target displacement and also shown that residual motion artifact was affected that the target velocity at each phase. Lastly based on this model, we developed simulation program and acquired similar results of target displacement compared with measured data. This research was supported by Leading Foreign Re-search Institute Recruitment Program through the National Research Foundation of Korea (NFR) (Grant No. K20901000001-09E0100-00110,) and the program of Basic Atomic Energy Research Institute (BAERI) which is a part of the Nuclear R and D Programs (No.20110006324) funded by the Ministry of Education, Science and Technol-ogy(MEST).