Feasibility of Using Ultrasound to Track Respiration Motion

1. Acquire 2D and 3D ultrasound images for 5 pancreatic cancer patients using the existing Clarity system with a hand-held probe. The visibility of pancreas, duodenum, and other organs will be evaluated. Based on this image acquisition experience, design and construct stands to hold the ultrasound probe. Issues to be considered in the design include (i) avoiding the stand and probe blocking radiation beams, (ii) avoiding ultrasound going through the ribs, (iii) minimizing the effect of respiration motion. Also explore building the probe into the immobilization device (e.g., Alpha cradle) or using robotic arm. 2. Acquire ultrasound images for 20 patients with pancreatic cancer treated in the Department of Radiation Oncology department using the tools developed in Aim 1. As the standard practice, the 4 dimensional CT (4DCT) and 4 dimensional (4D) morphological and physiological MRI (T1, T2, apparent diffusion coefficient, DWI) will be acquired for treatment planning, and a respiration-gated CT will be acquired immediately before the delivery of each fraction using an in-room CT or cone-beam CT for patient positioning. The ultrasound images may be acquired during initial simulation immediately before or after the planning 4DCT and the daily gated CT, and during the treatment delivery in 2D, 3D and/or 4D modes. All raw ultrasound data will be stored. 3. Process ultrasound data acquired above to evaluate the effectiveness of using ultrasound to image and to track pancreas/duodenum motion during the treatment delivery. The images will be processed to visualize pancreas and/or surrogates, such as the boundary between pancreas and duodenum, infusion catheter. To improve the visible appearance, elastography will be explored by processing the raw data collected in Aim 2. Existing software will be used, and may be modified if necessary, to segment and to register ultrasound with CT. A tool the investigators previous develop for multimodality registration will be used to register ultrasound with MRI. Anatomic markers, such as the boundary between pancreas head and duodenum, stent, infusion catheter, may be used for registration and/or motion tracking. 4. Develop/modify workflow and process to allow the final system to be used routinely by radiation therapists. If necessary, user-friendly software tools will be developed/incorporated in the final system. 5. Explore the use of Doppler mode for tissue characterization and the potential of using it to image radiation effects.