A method for tracking moving sources with PET

Stanford physical oncology researchers have developed a patented trajectory reconstruction method for tracking moving sources labeled with positron-emitting radionuclides using Positron Emission Tomography. The technique reconstructs the time-varying position of individual sources directly from raw list-mode data, bypassing conventional image reconstruction entirely. The Pratx lab studies how cells navigate the body's circulatory system using this non-invasive method. Applications include tracking of single cells in vivo, real-time tracking of a moving tumor during radiotherapy, understanding the efficacy of cell-based therapies, and estimation of respiratory breathing in 4D-PET.

(Image courtesy the Pratx Lab)
Figure 1 Single-source tracking. List-mode PET data from a point source (1, 10, 100, 1000 Bq) moving at 5 mm/s in an S-like pattern was reconstructed using a standard PET Maximum Likelihood Expectation Maximization reconstruction algorithm (top row) and the novel trajectory reconstruction method (bottom row). Results indicate the invention can track a moving source better than can be achieved using conventional MLEM.

Stage of Research
This algorithm can track a single cell inside a small-animal PET system with 2 mm accuracy provided that the activity of the cell (Bq) is greater than twice the square of its velocity (cm/s).

The Pratx Lab uses this approach to study metastasis in vivo, grow and image tumor models in the lab, enhance radiation treatments, and develop additional methods for tracking moving cells anywhere in the body of living subjects.