Poster — Thur Eve — 40: Evaluation of Respiratory-Induced Motion

Purpose: Collect statistics on respiratory induces internal motion to improve population based margin definition of target volumes and organs at risks and to determine the feasibility of screening patients that would most benefits from a 4DCT exam. Methods: Motion of relevant internal and external region of interest was evaluated on 4DCT datasets of 16 patients in an open study. Patients were selected based on tumour location. For a given 4DCT dataset, motion was characterized for each of 10 phases of the breathing cycle. Trace differences between two methods of respiratory signal acquisition were also evaluated. Results: Motion in the superior‐inferior (SI) direction, unlike other directions, showed a uniform motion trend between different structures. External markers have an opposed phase motion compared to internal structures. Diaphragm usually showed the largest averaged magnitude of motion (1.55±0.50 cm) with a wide range of amplitude. As can be expected, gastro‐intestinal tumors (0.88±0.27 cm) are in average less mobile than lungtumors (1.18±0.90 cm). Respiratory signal acquisition systems used for this study produced very similar traces regarding baseline variation and peak shape. Conclusion: Population‐based specific organs motion will be used for personalized treatment planning (e.g. delineation of margins, contours). Most structures have a similar shaped motion (i.e. no phase mismatch) and amplitude in the SI direction, except for external markers. Abdomen AP motion is a promising external indicator of internal motion magnitude.