Integration of Projection Profile Matching into Clinical MR Scanner System for Real-Time Organ Tracking and Image Registration

We propose integrating projection profile matching into a 1.5 Tesla clinical magnetic resonance (MR) scanner system to track a target organ in real-time for MRI guided therapy. As soon as a scanner acquires echoes, MR echo data are transferred immediately from the scanner to an “on-thefly” processing computer that executes projection profile matching, image reconstruction, image registration and motion correction, The system provides respiratory motion information about a target organ with a frame rate of up to 10 Hz and delay time of 200 ms. We report measurements of a phantom and a volunteer to evaluate the delay and the accuracy of the motion measurement with respect to the true motion, and feasibility. The study compares projection profile matching-based measurement and a “golden-standard” obtained by tracking a phantom with a video camera. The error was 1.5 mm with a delay of 200 ms. We tracked the moving liver of a volunteer, and two studies demonstrates that the system can be applied to clinical use.