Real-time Intraoperative MR Imaging Using Adaptive 4D Scan

A method of intraoperative real-time 3D imaging for magnetic resonance imaging (MRI)-guided surgery using newly developed “Adaptive 4D Scan” is proposed. Adaptive 4D Scan is an imaging technique to acquire a timeseries of volumetric 3D images (4D image) of a target organ over whole respiratory cycle, and by combining this technique with real-time navigator-echo-based target tracking, the proposed method offers real-time 3D visualization of respiratory moving target. The method consists of three steps: (1) acquire 4D image of the target through a respiratory cycle before operation, (2) detect patient’s respiratory phase by using navigator echo in real-time during operation, and (3) based on the respiratory phase detected in (2), extract corresponding 3D image from 4D image. We implemented Adaptive 4D Scan and integrated it with a 0.5 Tesla open-configured clinical MRI system for intervention. To asses feasibility of the method, phantom and volunteer study were performed. The mean position error in 4-D image of moving phantom was 3.1 mm, where the range of motion is 30 mm and number of 3-D images is 5. 4-D image of moving liver were also successfully acquired under near clinical condition. In conclusion, the study shows that the proposed method is feasible and has capability to provide real-time dynamic 3-D atlas for surgical navigation.